Category Archives: House Rules

It’s one thing to critique game mechanics, but sometimes you just have to make up your own.

Runequest in Glorantha: Home-brewed

With the launch just this week of RCQ – Runequest Glorantha – the “true” successor to the much loved Runequest 2, many of my geeky chums are once more venturing to Genertela to explore the deep mysteries of the cults, runes and deadly combat from back on the day.

So what better time for my dear friend Stephen (@smginnessuk) , GM of our Runequest 2 campaign, to share his house-rules for elevating an aged system for a more enlightened gaming age…

Introduction

I played my first game of Runequest in 1978.  I played it almost exclusively until it made it to third edition.  My lack of enthusiasm for the new edition, the stuttering publication of that edition along with a distancing of the game from Glorantha, and several life events meant that I rarely played the game between 1987 and just a few years ago.  That did not mean I stopped reading stuff or buying almost everything Glorantha that I could put my hands on.

I did play a lot of other games, including a variety of other Gloranthan related systems: Mongoose Runequest, Design Mechanism Runequest, Hero Wars, HeroQuest.  When I came back to RQII I fell in love with its simplicity all over again but there were things that rankled me, especially when I no longer had the copious amounts of free time to play, or to manage the detail of the second edition. Not to mention having been spoiled by modern systems that accommodate narrative gameplay and give agency to the players.

Now Chaosium just releasing a successor to RQII, I thought before I read the shiny new PDF that this would be a good time to show others how I adapted RQII and imported things from other iterations of Glorantha to allow me to play Runequest now.  This is my first real attempt to do this and it will change and adapt to my players responses, its inability to cope with at the table situations and new cool ideas that I come across.

The main changes I’ve made fall into three categories:

  • Character design
  • Running the game
  • Heroquesting

The latter two will follow in a day or two. But, to kick things off…

Character Design

Characters are rolled and written up using pure RQII, just like I did it in 1978. Statistics, modifiers, spells and skills. I add the the previous experience rules to get more experienced starting characters, but that is as far things go there.

I do not use the old character sheet, but have designed my own, one based on the Heroquest way of doing things and designed to put the key information front-and-centre in a way that really supports play at the table.

Gundrig-RQ1-page-001

Skill Groups

This is where things start to change a little. Skills are organised into three key skill groups.  This is often narrative background things like “Pavis born and bred”, “Initiate of Orlanth” or “Experienced scout” with all of a character’s skills organised underneath those.  Each group is then assigned a skill level based on the best five skills in the group.  The skill groups have threshold numbers: 15%, 30%, 50%, 70%, 90% and 120% which I assign the titles used in the Robin D. Law’s King of Dragon Pass game: Fair, Good, Very good, Excellent, Reknowned and Heroic.

All skills that fall into the group are then treated as operating at at least the threshold skill level.

The upshot is that a character with Good “Pavis born and bred” can tell the GM at any time that someone born and bred in Pavis’ dusty streets should be able to find a decent short cut to Gimpy’s and use 30% as a chance for that.  The player might then list “Pavis backstreets” at 30% on the sheet and, if successful, give it a tick for later experience checks.  It is a way of providing a broad base to skills and allowing players to more effectively play the character they envisaged without having to think of every little skill they might need.

Gundrig-RQ2-page-001

The other aspect of skill groups is that once five skills within the group have advanced beyond the next threshold, the threshold goes up and so every skill goes up to the threshold.  E.g. a Good “Initiate of Orlanth” has just raised his broadsword attack to 70%.  Within this skill group, he already has Spot Hidden at 85%, Riding at 80%, Evaluate Treasure at 70% and Camouflage at 75% (all skills the player and GM agreed fitted within this skill group).  As broadsword attack was the fifth skill in this group to get to 70%, the skill group is now Very Good and all skills within it – including any new skills the player comes up with in play that fit within this this group – will be at 70%.

This reflects the idea that during down time, when they are living their lives rather than adventuring, characters maintain and update the skills associated with that life.  Initiates of Orlanth will find themselves using skills that such initiates use on a regular basis.

Next-up: Running the Game (coming soon!)

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D&D5 – Mucking about with Proficiency

One of the simplifications that lies at the heart of D&D5 is the Proficiency mechanic: one central value, derived from Character Level, added to your die roll. Whether you’re hitting stuff with a pointy stick or trying to remember the name of that ancient carbunculous statue: roll 1d20 and add Proficiency.

So obviously, that’s RIPE for complication!

So here’s a few proposals on how you can muck about with Proficiency, adding complexity and individuality without breaking the game (too badly!)

 

Proficiency: the five core functions

To begin with, let’s split Proficiency into its main functions:

  • Skill rolls
  • Saving throws
  • Spell-casting rolls
  • Combat (and here I’d suggest further diversifying into Melee Combat and Ranged Combat)

Every character will now have five separate values to represent their relative skill in different areas. So, as a Barbarian you may favour Melee Combat, Saves and Skills; as a Wizard you’ll want to focus as much on Spell-casting; a Bard may go with a more even spread.

Now for deriving and increasing these values. Here’s a few ideas:

Method 1: Simple Level Proficiency

All values start at +2. You get +1 to one Proficiency value of your choice at Level 1 and every level thereafter. You can’t add more than Level / 3 to any one value (rounded up to 1 for L2, with an absolute maximum of +8).

This allows a generalist character to have +6 in all five areas by L20, or a specialist to have a spread of +8/+8/+8/+3/+3.

A simple progression and easy to manage, but leads to over-powered specialists.

Method 1A: Capped Maximum

All values start at +2. You get +1 to one Proficiency value of your choice at Level 1 and every level thereafter. The highest value must be within 2 points of the lowest value.

This reduces the ability of a Specialist to run ahead, with a maximum spread of +7/+7/+7/+5/+5 at L20.  However, it does allow someone to have +4 to one ability at 2nd level. Almost certainly not game breaking, but does stretch the underlying assumptions of the mechanics a little.

Method 2: Points-buy

Each level you get a number of Proficiency Points equal to the new Level (i.e. at 3rd level, you get 3 points). Increasing Proficiency values costs as follows:

Value +3 +4 +5 +6 +7 +8
Cost 2 8 15 25 50 100

You can only increase 1 value per level. This allows for the following progressions:

  • Generalist:  focusing equally on all Proficiency values, you get +1 to one Proficiency value every level (except 18th). At 10th level you have +4/+4/+4/+4/+3 and end up with +6/+6/+6/+5/+5 at 20th level.
  • Ultra-specialist: focus on a single Proficiency, you hit +6/+2/+2/+2/+2 at 10th level and +8/+2 etc. at 20th level. Good luck with those Saving Throws…
  • Dual specialist: 10th level is +5/+5/+2 and 20th level is +7/+7/+2.
  • Priority 3: +5/+4/+4/+3/+2 at 10th, +7/+6/+6/+4/+2 at 20th
  • Focus 4: +4/+4/+4/+4/+2 at 10th, +6/+6/+6/+6/+4 at 20th

More granular, more choice, but complex book-keeping. And in reality, would anyone not go for something akin to Priority 3 or Focus 4? Might be better just defining some possible progressions at Level 1 and having players pick them.

Method 3: Class-based Proficiency

If you’re going to define Proficiency up front, why not just set it by class a la D&D3.x?

Firstly, change the default assumption back to 4 Proficiency types, dropping the split between Melee and Ranged combat. Set four core progressions:

  • Strong: +3 at 4th level and further +1 every 4 levels, until +7 at 20th
  • Standard: as per usual
  • Moderate: +1 at 1st level, +2 at 2nd level and +1 every 4 levels until +6 at 17th
  • Weak: +0 at 1st level, +1 at 2nd level and +1 every 5 levels until +4 at 17th

Then allocate classes one of two possible arrays:

  • Specialist class: Strong, Standard, Moderate, Weak
  • Generalist class: Standard, Standard, Moderate, Moderate

E.g. A Fighter would be Strong Attack, Standard Save, Moderate Skill, Weak Magic. A Bard could be Standard Magic, Standard Skill, Moderate Attack, Moderate Save.

Method 4: Simple Proficiency, revisited

Start with spread of +2/+2/+1/+1/+1. Maximum value of any Proficiency is 3 + Level /5 (rounded-down). Add one point to one Proficiency value as Method 1. At 5th level, a specialist could be +4/+3/+2/+1/+1. But by 20th level it’s evened out at +7/+6/+6/+6/+1.

Why put this last, rather than as Method 1B? Well, because if I were to implement one of these ideas, this is the one I’d go with. Balances customisability with simplicity. What’s not to like?!

Wizard’s Duels

I’ve always felt that most F20 fantasy rulesets fail in one regard in particular – the ability to have exciting magical duels, where two wizards match off in a flurry of arcane energy. So, inspired by Ars Magica’s certamen, here is a detailed option tailored for D&D5 but easily tweakable to any F20 game.

Wizard’s Duels – Why do they happen?
In any given location, there is only a limited amount of arcane energy waiting to be tapped. With limited resources and almost unlimited magic-user ego, when two arcane spell users come into contact, a wizard’s duel frequently is the result.

  1. Limited Magic Metaphysic: When two or more arcane spell-casters are in close proximity, the same encounter and within 100’ of one another, their ability to draw on their full magical resources are reduced. Spell damage dice are reduced by 1 step (e.g. d8 to d6), targets of arcane spells have Advantage on any Saves and spell Durations are reduced by 25%.
    Why have a duel? Because you’re less use to your party if there’s an enemy Wizard flying around.
  2. Magical Offense: As a result of their delving into matters arcane, all Mages are surrounded by an innate magical field. This has no effect most of the time, although it does mean that powerful spell casters can be identified through Detect Magic spells and abilities. However, if a spell-caster is targeted offensively by an enemy spell-caster, there is a chance that their magical aura will flare up and trap both casters in a magical vortex, forcing a Wizard’s Duel to take place.

Vortex Check: Caster rolls Spell Attack roll vs DC of 15+ Levels of any active spells on the Opponent Caster (excluding Spell Protections, see below)
Both Wizards are of the same Tradition: +2 to DC
Opponent has raised their aura: + Opponent Caster Level to DC

Caster Level and Active Spells both contribute to the strength of the opponent’s magical aura, a stronger aura making it more likely that a vortex is created. However, a higher level attacking spell is more likely to be able to bludgeon its way through the aura.
Why have a duel? Because magic makes it happen!

Spell Protections: if the target has protection up that defend against spells attacks (e.g. Globe of Invulnerability), that protection sits outside of the Wizard’s natural magical aura. As such, the Vortex check is made only if the attacking spell penetrates the defensive spell.

Raising Aura:  A Target Caster can use a Reaction to consciously flare up their magical aura to increase the chance of invoking a duel. To do so, they must be aware of the enemy caster and that a spell is being cast (e.g. they observe verbal, somatic or material components being used, or they see the trajectory of the spell). Alternatively, as a Bonus Action, a Caster can intentionally heighten their aura so that any incoming spell invokes a Duel, even if they are not aware of it. An aura heightened in this way remains heightened until the caster’s next turn.

  1. Invoked Duel: A Caster within 30’ of an enemy caster can Invoke a Wizard’s Duel. No roll is made, and the Opponent cannot prevent the Duel from starting.
    Why have a duel? Sometimes it’s not up to you

MAGICAL VORTEX
A Wizard’s Duel takes place within a magical vortex that exists outside of the prime material plane. Neither the participants nor the vortex itself can be harmed, dispelled or affected by any means by any denizen of any of the known planes. The vortex manifests itself as a crackling storm, which may reflect the personalities and magical strengths of the participants or the inherent magical aura of the place in which the vortex was invoked. Both participants can be seen by any outside observers, although in reality this is a shadow manifestation of their true selves. Observers may also see visual representations of the Wizard’s Duel that correspond with the magic schools or specific spells being used in the duel.

THE DUEL
Duels take place in Rounds, in parallel with any action taking place in the real world. The wizards hurl magic against each other in a show of brute force, with the aim of overcoming their opponent and neutralising their magical energy.

  1. Duelling attributes: Both Casters retain their previous Initiative score. However, for the purposes of the Wizard’s Duel all actions are considered simultaneous. Each caster has a Magic Point score, equal to their normal maximum hit points.
  1. Each round, the participants each select a spell, giving consideration to Spell School and Spell Level. In a Wizard’s duel, the effect of the spell itself is not relevant, as the duel is fought using arcane energy in its pure distilled form. This selection is done in secret and then revealed simultaneously. That spell is marked off as having been cast. If necessary, the player should also declare whether they are aiming to cause damage or invoke a special effect (see below).
    Burning Spent Slots
    A Wizard who has cast memorised spells before the duel begins retains some of the essential essence of that spell in their magical aura. Instead of using a memorised spell, a Wizard can opt to use a Spent Slot. To do so, the Wizard must take Hit Point damage equal to 1d4 + Spell Level. If this damage reduces the Wizard’s HP to 0 or less, they fall unconscious and the duel ends. This option is only for spells cast prior to the duel begins, and cannot be used for spells cast during the duel itself.
  2. The participants roll Duel Score on 1d20 + Spell Attack + Spell level, modified as below .
School Offensive Total Defensive Total Other Effect
Abjuration -1d6 +1d6 Damage Magic Points
Conjuration Adv Damage Magic Points
Divination Damage or Special Effect: Assess Power
Enchantment Damage or Special Effect: Fascinate
Evocation Damage Magic Points x2
Illusion Damage or Special Effect: Distract
Necromancy Damage or Special Effect: Drain
Transmutation Adv Damage Magic Points
Universal Damage Magic Points

If the Offensive Total is higher, the Active Caster achieves the Effect detailed in the table above. For some schools, the caster must choose whether they are seeking to cause Damage or to invoke a special effect. This should be declared before the character rolls their Duel score.

NB: For Abjuration, roll 1d20 and 1d6: subtract the d6 for the Offensive total, add it for the Defensive total. For Conjuration and Transmutation, roll 1d20 for the initial total and a second d20 for the Advantage, using the higher value for the Offensive (Conjuration) or Defensive (Transmutation) total as appropriate.

Damage: Roll 1d6 + Caster’s Int + Spell Level – Opponent’s Wisdom save. If the damage total is greater than 0, the Opponent must choose one of the following:

  • Apply the remainder as damage to their Magic Points, or
  • Discard their highest level memorised spell, or
  • Dispel their highest level active spell.

If the Opponent’s Magic Points total is already at zero, they must discard either a memorised spell or an active spell or concede defeat.

Special Effects: The opponent suffers an effect as follows:

  • Assess Power: See below
  • Fascinate Opponent: Advantage to Defensive total next round
  • Distract Opponent: Advantage to Attack total next round
  • Drain: Opponent suffers 1 ability point damage to INT or WIS (Attacker’s choice)

In addition, if the Offensive Total is 10 or more points over the Defensive Total, the Opponent also suffers Damage as above.

Duel Score Assess Power Result
0 Total number of spell levels currently memorised by Opponent
+2 As above, plus the school in which the caster currently has the most spells memorised. Also reveals the caster’s Tradition
+4 As above, plus number of levels in that school.
+6 As above, plus all other schools in which the caster has spells currently memorised, in order of most to least.
Every extra +2 Number of spell levels in each school, from most to least. Once all schools and total spell levels are revealed, the Active Caster learns how many Spells are currently memorised plus how many levels of Spent spells there are for any school of their choice.

Once all schools and total spell levels are revealed, the Active Caster learns how many Spells are currently memorised plus how many levels of Spent spells there are for any school of their choice.

Conceding Defeat: At any time, either caster can offer to concede defeat to their opponent. Their opponent is not obliged to accept and can force the duel to continue. If they accept, the duel ends. The Caster who accepted the defeat is the Victor, the Caster who conceded is the defeated Caster, regardless of the relative positions in terms of spells remaining and Magic Points.

ENDING THE DUEL
The Wizard’s Duel ends when one of the following conditions is met:

  • one or both Casters Magic Points reaches zero and they have no more memorised spells remaining
  • one Caster concedes defeat and the other Caster accepts
  • either Caster’s Hit Points total reaches zero.

If both casters meet one of the ending conditions simultaneously, the duel ends with no Victor.

On ending, the stormy vortex abruptly stops and each caster is returned to their starting location, dramatically but without further harm. No further magical duel is possible between the two individuals for the next 48 hours unless both Casters explicitly agree, in which case the Victor gains Advantage to all Duel rolls.

TO THE VICTOR THE SPOILS
A caster with memorised spells and/or Magic Points remaining is the Victor. They have the opportunity to learn from their experience of the duel:

  • A Wizard may add any one of the spells used by their opponent to their spell book. This must be of a level and school that they could normally cast, and must be scribed into their spell book within 12 hours of the duel ending.
  • A Sorcerer may replace any of their currently Known spells with one of the spells used by their opponent to their spell book. This must be of a level and school that they could normally cast. This occurs immediately.

In addition, the Victor can ignore the presence of the defeated Caster for the purposes of the Limited Magic metaphysic for the next 48 hours.

PRICE OF DEFEAT
It is possible that the losing Caster still has some spells (or spell-like abilities) remaining. They are free to use these as before. However, any spell cast within 100’ of the Victor and any ranged or area-effect spell cast targeted at a point within 100’ of the Victor has a 50% Arcane Failure rate, and is cast at 50% damage / Advantage of Saves / 50% duration for the next 48 hours.

 

NB: This is tweaked from an idea I put together a few years back for D&D3.5/PF, so it may be I missed making a few of the changes necessary to fit with D&D5. However, with relatively minor adjustments it could be used for any RPG magic system that has the feature of limited spell casting ability, whether it be Power Points, Mana, Spell Slots or whatever.

Skill Contests

Many RPGs are fundamentally skill-driven, using successes in character talents to adjudicate action, create uncertainty and drive the story forward. On occasions, the story might develop in such a way that a skill takes centre stage – can the hero defuse the bomb before the City is levelled? Can he repair the damaged controls before tdisarm a bombhe light aeroplane plunges into Mont Blanc?

For fighting, we have combat systems. For social interaction, we now have a number of social combat systems such as those offered by Luke Crane’s Burning Wheel and Green Ronin’s A Song of Ice & Fire. But for extended skill contests, the RPG world is decidedly under-resourced. You have options like extended checks (multiple successes to complete), but this is often nothing more than rolling a single skill lots of times. Dull, dull, dull. It lacks the interesting element of good combat-type systems, which is that of tactical choices.

Going back to the Infiniverse of the 90s
Probably the best system I’ve seen is West End Games classic system Torg (recently spotted resurfacing on Bundle of Holding to the delight of fans like me).

Torg breaks dramatic skill tests into up to 4 stages: A, B, C, D, which represent 4 specific steps that have to completed in order to achieve the task (e.g. A: Open the outer casing; B: Analyse the circuits; C: Disarm the booby-trap; D: Cut the fuse wire). Torg drama deckTorg’s custom initiative cards then set the pace for completing the task. Each round, the initiative card will list some combination of those 4 letters or state “Complication”. Each round, the player has a real tactical choice to make:

  • Is there more than 1 letter that I need? In which case, should I try to complete multiple elements while I can, or play safe and just go for a single success?
  • Are there no letters that I need? Should I make a check to gain a bonus to my next attempt, or try to complete a letter than isn’t there? (at substantial penalty)
  • How much time is left? Should I just go for it and hope I succeed? (“Just cut the red wire!”)
  • If it’s a Complication, you need to succeed at a roll, or something bad happens (“Oh no, my pliers fell down the lava-filled chasm!”) – lose a step, increase the difficulty of future steps, or require the character to switch to a new skill.

The cards also count as the timer, with the GM deciding how many card flips are available before the consequence of failing the task comes about. Communicating the reducing time to the players is tricky, but essential to build the sense of impending doom (and sometimes you can just be open about it – a little bit of transparency can sometimes add more tension not less!)

Problems with Torg’s Dramatic Skill Resolution
This is a relatively easy system to port across to other RPGs, although it works best with games that allow multiple actions in a single round – without that a key element of tactical choice is removed. One issue is the reliance on the initiative cards to generate the A, B, C, D results. A possible fix is to roll 4 different coloured dice at the start of each round, with every die that is above a certain value meaning that task can be attempted. If none of the dice reach the Threshold, it’s a Complication. This actually adds more flexibility than the Torg cards, as you as GM could control the rate at which certain tasks are possible – ramp up the tension by making that key D stage only crop up 20% of the time.

Another downside is that it can be sometimes difficult to fit the narrative to the game mechanics. The best way to resolve this is to make sure a specific task is ascribed to each letter, and then improvise why certain things aren’t possible, especially if the scene is ripe with environmental or other hazards (as should be the case for a dramatic skill check). Why can I not analyse the circuits this turn, but I could disarm the trap or cut the fuse? Well, you try to concentrate on the circuit layout but are distracted by a nearby explosion or roaring T-Rex.

A new approach – Skill Combat!
There’s another possible approach to spice up Skill Contests that as far as I’m aware no game has yet embraced. To go with Physical Combat and Social Combat, we have Skill Combat!

Each round, you try to cause damage to the task’s Difficulty Points. This is largely the same as how many RPGs treat extended skill checks at the moment – you roll against difficulty and have to accumulate a certain number of successes. You could go with fixed skill damage, or inflict the difference between the Target Number and your result. For class-based games such as D&D, I’d be inclined to go further and give each class a Skill Damage die to reflect differing ability (so a Rogue does d10 skill damage, a Fighter or Wizard only d6). Otherwise this is a relatively straight-forward idea.

However, this is the new bit. As with any combat, the task also tries to cause damage to you in return. If the game has an existing mechanic to represent narrative defeat – such as Fate or HeroWars – use that. For something like D&D you could add a new characteristic for skill hit points (e.g. “Composure”), along with another characteristic (e.g. “Cool”) that represents your Skill Armour Class. Each round as you attack the Task, the Task attacks back, trying to hit your Cool and undermine your Composure. The amount of damage done by the Task is probably a little abstracted, based on the overall stress of the situation: it’s not about how much time is left, it’s about how much pressure the PC perceives themselves to be under. Again, in a d20-style game, it’s pretty easy to come up with suitable values.

If the Difficulty Points reach zero, you succeed against the odds. If your Composure reaches zero, you run away screaming, throw your hands up in the air claiming it’s just too damn hard, or whplane mountainsatever. In effect, this gives you a dual timer track – will the hero repair the aeroplane controls, will the plane crash, or will the hero reach breaking point and run for a parachute in a (futile) attempt to save herself?

Because this system introduces the dual nature of attacking and being attacked, it opens up the opportunity for slightly crunchy tactical options. This changes extended skill contests by adding a critical missing element – player choice. It’s no longer just roll your skill. Do you decide to Taking Care (reduce your chance of success, but minimises your risk of losing Composure)? Do you tackle the task Recklessly (reducing your skill, but boosting the Difficulty damage you inflict)?

Conclusion of sorts
Of the two options I describe here, I think there is more utility in expanding the Torg system to other games. But I think there could be some mileage in developing a Skill Combat system as an interesting counter-point to the usual way of doing things. Consider the gauntlet thrown down

Advantage to the Max!

As I discussed previously, Advantage is the powerful yet simple super-mechanic that sits within D&D5, providing an easily managed impetus to drive the game in whatever direction the DM wants to go: if not its beating heart, then certainly a clean well regulated kidney or perfectly functioning non-cirrohtic liver. No, I don’t think that metaphor works particularly well either, but feel free to take it and use it yourself all the same, no need to thank me.

The simplicity of Advantage, for some, may also be its weakness. For those gamers who like a little crunch from time to time, the Advantage mechanics are a bit of a one-trick pony. If things are good, you get Advantage. If things are bad, you get Disadvantage. If things are, well, complicated, you get nothing. Simple, yes, but not especially nuanced. However, another of the great things about Advantage is it is actually extremely resilient to being messed around with. Here are a couple of suggestions as to how you can take Advantage to the max.

 

2D20 GOOD, 3D20 BETTER – DOUBLE ADVANTAGE

If you want to reflect a situation where the cards really are stacked in one character’s favour, one easy house-rule is to throw in an extra d20:

Double Advantage: roll 3d20 and take the highest result.

I’d suggest this can add value in your game in some very specific circumstances:

  • Stacked Deck – a character has Advantage from 3 or more sources. E.g. they’re attacking with Help from a colleague against a Blind opponent who has been Stunned.
  • Did I crit? – The die roll could have some bearing on the situation that isn’t just success or failure. E.g. in combat, you might want to know if a blow is a critical hit or not.
  • Failure is an option – the odds aren’t so stacked in that character’s favour that you just automatically give them the most favourable result possible.

When not to use Double Advantage? If there’s no time pressure and no consequences for failure, don’t roll at all. Ever. Just don’t waste everyone’s time. Don’t turn our beautiful game into a dumb exercise in dice rolling.

Don’t show me the odds
Double Advantage has a relatively modest impact on the probabilities:

  • The odds of rolling <4 are pretty small in both Advantage & Disadvantage
  • Advantage gives you an 80% of rolling 10 or better. Double Advantage makes it 91%, the equivalent of another +2 modifier
  • Advantage will get 15 or more 51% of the time. With Double Advantage its 66%
  • Advantage has 9.8% chance of a natural 20. Double Advantage increases this to 14.3%

Advantage Prob 1 You can also check out the non-cumulative probabilities here: http://anydice.com/program/4704

Complicating what is simple
Of course, if you’re interested in taking a simple rule like Advantage and turning up the crunch level, there’s probably another Advantage rule that you’ve already discarded. That’s the rule that says any situation that has both Advantageous and Disadvantageous factors is resolved with a straight d20. It’s a rule with zero impact on any probabilities, it’s just there to keep things clean, simple and tidy. If you can handle a bit of untidiness in your game, just go for it. Not that you need my permission!

 

EXCEEDING YOUR LIMITS – BOOST

As I’ve said before, Advantage increases your chance of success, it doesn’t make success possible where it otherwise wouldn’t be. If that doesn’t sit right with you, you follow the D20 system Modifiers Golden Rule: dish out +2 or -2 as you see fit. Having said, that’s not really D&D5’s style. The Bless spell, with a hint of Cortex system, points to a better, more interesting way:

Boost: a character who has a Boost rolls an addition d4 and adds the result to their total. If you already have a bonus die from some other effect, e.g. Bless, roll this in addition to the boost die and take the highest.

You should apply Boost where something both makes an action easier for a character and makes it possible to exceed their normal limits. E.g. when one character uses the Help action by distracting their mutual opponent to create an opening, instead of awarding Advantage it may make sense to award a Boost. Similarly with the Working Together rules outside of combat: if the party ties a rope around the portly Wizard and gives him a bit of a tug to help him leap the crevice, they’re not just helping him achieve his maximum potential, they’re trying to push him beyond his limits. Award a Boost. Hell, maybe award an Advantage AND a Boost!

To see how this looks, see updated graph below. In terms of probabilities, outside of values <4 or >20, a single boost just increases the score by 2.5, the mean score for a d4, for any given probability. E.g. instead of 50% chance of getting 11, you have a 50% chance of getting 13.5.

Advantage Prob 2

As for Advantage plus Boost. Well, that’s the best option of all for near guaranteed success. And you know what, if you want keep stacking it on, you go for it. Even rolling 5d20, the 22% chance for a critical means there’s still plenty of uncertainty to help keep things interesting.

 

CONCLUSION

In summary, if you want to crunchify the Advantage rules, there are three immediately obvious options:

  • Allowing for super Advantages of 3d20 or even more
  • Scrapping the rule that says any number of Advantage + any number of Disadvantage cancel each other out
  • Replicating the die-based bonus from spells like Bless for more general modifiers such as team work bonuses.

Although they all add complexity, none of these will do any harm to the fundamental probabilities built into the system. So if you like crunch and you miss the stacking modifiers of 3rd edition D&D, you can easily replicate that style of play in D&D5 without breaking the game.

Caveat: there is one class that disproportionately gains from the Double Advantage house rule. With an increased critical range, the Champion sub-class of Fighter would benefit more than any other class from multiple Advantage. E.g. a crit range of 19-20 is 8% more likely with Double Advantage, compared to just 5% more likely for a natural 20. Game breaking? Probably not.

 

So what do you think, loyal, intelligent and charming reader? Is this something you’d consider adding to your game, or mere statistical frippery?

Please feel free to leave your comments below or send your thoughts, considered or otherwise, via Twitter @thedicemechanic

Edited 24th September: added Conclusion & Caveat. Corrected a typo, graph titles and ended probability curves for d20 rolls at 20.