The Aurora RPG Engine – Part 6


Handling Difficulty and Modifiers

As already noted for the reasons mentioned above, the baseline difficulty of a task as well as pertinent modifiers are handled by adjusting the dice pool, adding or subtracting dice in ½d increments.  The target number (15) remains the same.

Nomenclature.  What to call this up and down travel through half dice increments?  While there are many nice and elegant names that can be chosen to fit and reinforce the genre, theme, and tone of a specific campaign, in this document I will generically refer to it as stepping up and down the dice or difficulty ladder.

Setting Difficulties:  The Difficulty Ladder.  To borrow the approach commonly used across many (and perhaps most) RPGs, a task’s difficulty is set and handled by the GM determining the baseline difficulty based on a descriptive chart:

Task Difficulty Pool Modifier Modifier in Steps
Trivial +2d 3 to 4 steps
Easy +1d 1 to 2 steps
Routine +0d No change
Challenging -1d 1 to 2 steps
Intense -2d 3 to 4 steps
Formidable -3d 5 to 6 steps
Severe -4d 7 to 8 steps
Insane -5d 9 to 10 steps
Herculean (Heroic/Epic) -6d or greater 11+ steps

(Just another reminder that, compared to most other games, it is the character’s dice pool that is adjusted via stepping rather than setting a base target number.)

For a more “narrative” style of play (as is done, for example, in the FATE system) this same chart and nomenclature is used to set both the baseline difficulty as well as any situational modifiers.  Here, the table serves double duty in a conversation between the GM and the player(s) to determine the final difficulty:  “You are going to jump across the wide ravine while it is dark and raining, but you have a good running start and are wearing your lucky underwear.  Still sounds quite formidable, step down 5 or 2½ dice.”

Using a more “traditional” procedure, once the baseline difficulty is determined (using the baseline difficulty chart) the total pool is further adjusted using modifiers from a list of standard situational modifiers – for example, Lightly Obscured = -1 shift; Heavily Obscured = -3 shifts; Totally Obscured = -5 shifts.  With a robust and extensive enough list of modifiers, a very granular game system can easily be created if appropriate and desired.

Either way, there is no need to re-invent the wheel, and the familiar difficulty-setting method can be used in Aurora’s core resolution engine quite easily.

Easy and Trivial Tasks?  It is recommended that skill rolls be called for only when a task requires some degree of skill or ability to do properly (following directions on a map in a city as a tourist is generally not a skill roll), is narratively interesting (there’s something relevant that can arise from failure or there is something to be gained knowing how well a task is performed) and/or there is something out of the ordinary or dramatic about the situation.  Thus, though they are on the list, Easy or Trivial skill tests are likely to be infrequent except in unusual circumstances or when circumstances inject extra adversity and thus uncertainty.  Then again, adventurers often find themselves in very unusual circumstances while also under duress so… maybe in the end Easy/Trivial rolls won’t be that infrequent (albeit often with a lot of other modifiers piled on top).

Setting Difficulties:  Using Traits, Aspects, and Tags.  That said, if we want to add new wheels to the idea, the notion of modifiers can be expanded to invoke the idea of Aspects or Traits as detailed in this earlier blog post and as used in games such as FATE and Modiphius’ Star Trek Adventures.  To briefly summarize the linked blog post, a Trait, Aspect, or Tag is a phrase or label that describes and denotes something (usually out of the ordinary or special) about a person, object, or scene to which it is attached.

If a case can be made that the Trait or Aspect applies to the action/event, then it may affect a test/roll in two ways:

  • It may allow (or disallow) something that normally would (or would not) be possible.
  • It may affect the difficulty of the task, adding or subtracting dice to the pool depending whether it helps or hinders.

Using this idea, there is no list of standard situational modifiers.  Instead, once the base pool is determined, any and all applicable Aspects, Traits, or Tags are factored in one by one until the final dice pool is created.  How much of a modifier each Trait or Aspect provides to making a test depends on how relevant or important it is and its magnitude of impact.  Some of these will be highly situational, while others, such as the strength of a lock or the impact of fog, will be more common within a more fixed range.  These can be noted on the table with a card denoting the magnitude (and thus number of shifts) using dots or boxes next to the Aspect.  For example:  Lock ■ ■ □ (where each filled box is a full die, and a white box is a half die), or Lock ●●●●● (where each dot is a step).

Altogether, this provides greater flexibility and range of effect than a set table of modifiers, making for a richer set of choices and enhancing player involvement.

The Double-Edged Nature (In a Good Way) of Traits.  One of the nice things about applying Traits, Aspects, or Tags (versus a rigid list of modifiers) is that many of them will be of a dual nature, acting alternately as hinderance as well as able to be leveraged for advantage by the characters.  For example, while a Trait of “Very Foggy” makes it more difficult to aim and therefore more difficult to hit things in ranged combat, at the same time the fog makes it easier to sneak around or to stealth away.  More creatively, if I’m on fire, I can leverage that trait to more easily put out the flames as everything around me would be damp.  (Still, it’s likely best advised to avoid being set on fire in the first place…)

This double nature becomes even more important if the Aspect, Trait, or Tag is part of a character’s background, concept, values, disposition, or similar.  As in FATE, Cortex Prime (using Distinctions), and to an extent in Star Trek Adventures (using Values), traits can be used to both aid and appropriately hinder a character to create interesting narrative situations and complications while fostering greater RP opportunities.

How to Handle the ½d to Avoid Confusion.  How best to remember which die in a pool is the ½ die (d3) and avoid the (almost inevitable) “Wait, which one was it?” conversation?  As no more than a single ½d is ever required as part of a pool, here are a few options:

  • Each player chooses a die, unique in some way (colour, style, size, etc), to always be their ½ die.
  • Set a table rule, for example, “Blue dice are always counted as the d3.”
  • A single die is designated as the d3 die, to be shared by all the players.
  • The group invests in buying (or 3D printing) a few of the fancily-shaped d3s that are available on the market, and use those when rolling a ½d.


Baseline Values and an Aside on Probabilities
| Index |
The “Extra Die” Beauty: Creating a Margin of Success

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