As talked about in “Chapter 5: Playing the Game” in the Playtest Players’ Guide, CORE20 uses three different mechanics to represent the benefits a character can earn on skill checks, attack or defense rolls, or challenge throws or saving throws — bonuses, boons, and advantage. None of these are concepts new to the game, but the way the game makes use of them evolved out of multiple years of the alpha playtest — and from my matched states of dissatisfaction with how complicated bonuses were in 3.5e D&D, and how advantage in 5e D&D doesn’t really work as a one-benefit-fits-all attempt to replace bonuses.
Typed Bonuses
The 3rd edition of the D&D game was a genuinely remarkable attempt to codify the baseline mechanics of 2nd edition and 1st edition AD&D into a modern, more logical ruleset. The thing I admired the most about 3e (and specifically the 3.5e update which is the version of 3rd edition most people know) was how the underlying math of the base attack bonus, base saving throw bonuses, hit points, spell damage, and much more was lifted directly from AD&D. The presentation was very different — and much improved — even as the numbers crunched exactly the same way. But across all the many areas where 3rd edition excelled at evolving two-decade-old rules into a more robust setup, its solution for handling bonuses might have gone a bit too far.
One of the problems of AD&D was that bonuses to your d20 rolls all generally added to each other. This meant that savvy players could pretty easily power-game their way into ridiculous modifiers with the help of spells, magic items, and judicious choices of class and ancestry. But 3rd edition solved that problem by creating named types of bonuses, with the idea that you couldn’t stack or add together multiple bonuses of the same type — you only got to use the better bonus. For example if your armor gave you a +2 armor bonus, you couldn’t add the +1 armor bonus from a magic item like bracers of armor.
It was amazingly straightforward! Except for the small issue that 3.5e came with seventeen different types of bonuses: Alchemical, Armor, Circumstance, Competence, Deflection, Dodge, Enhancement, Insight, Luck, Morale, Natural Armor, Profane, Racial, Resistance, Sacred, Shield, and Size bonuses. [Pauses for breath.] Oh, and the rules were just kidding about not being able to stack bonuses of the same kind, which you could do sometimes but not at other times.
Anyway, it was complicated.
Free-Range Bonuses
The first two versions of the CORE20 alpha playtest rules — version 0 in 2010 and version 1 in 2013 — were effectively the core feat setup of the game layered in on top of the D&D 3.5 ruleset. As such, the earliest CORE 20 campaigns hewed to the typed-bonus line with all its weird complex simplicity. Starting with version 2 of the rules in 2014, though, we tried a little experiment where we kept the setup of 3.5e but lost typed bonuses. Everything in v2 was just a bonus, and all bonuses stacked, working with the idea that without regular class-based increases to attack bonuses, saving throw modifiers, and so forth, stacking bonuses wouldn’t be as unbalancing in CORE20 as it was in 3.5e.
This change worked as intended, letting things like the bonus to defense modifier from the shield of faith spell and the bonus to defense modifier from the protection from evil spell (both deflection bonuses in 3.5e) add together. But inevitably, through version 3 of the alpha playtest (2016 to 2019), the problems of free bonus-stacking in AD&D made their way into the game, giving characters the opportunity to stack up combat modifiers in ways that were just a bit too sweet.
The Dice Have It
Porting the roll-two-d20s-and-take-the-best advantage mechanic of D&D 5e into CORE20 was something I’d thought about right from the point when I was working on the 5e core books in 2013 and 2014, alongside version 2 of the CORE20 rules. And even though I rewrote a few sections of those rules a couple of times to incorporate advantage and see how it felt, I always went back to bonuses. I loved advantage as a mechanic, and thought the idea of replacing a ton of numerical bonuses with an extra die roll was a great fit for 5e D&D. But 5e is a game that flattens its math drastically compared to the 3.5e ruleset that CORE20 was initially carved out from, meaning that CORE20 works a lot better with a wide array of bonuses that would break the math of 5e in short order.
Boons (along with banes, their penalty counterpart) originated in the excellent game Shadow of the Demon Lord by Robert J. Schwalb — one of the best game designers of all time, and one of the first designers I got to work with directly when I started working in RPGs in 2004. A boon or bane is a smaller die that you roll alongside a d20 and add to (or subtract from) that d20 roll. Interestingly (to me, anyway), D&D 5e kind of uses the idea of boons and banes, but doesn’t name them as such. Spells like bless, features such as Bardic Inspiration, and many more places in the 5e rules see players adding the roll of a d4, a d8, or what have you to a d20 roll, but 5e doesn’t go the extra distance to make boons and banes a consistent mechanic.
As with advantage, I liked the mechanics of boons and banes a lot when I first read them. And I especially liked what I’ll call the “tactile memory mechanic” that boons and banes create. For me, as I know is true for many players, remembering short-term bonuses is really, really hard. Anytime I have two or more bonuses that I need to remember, it’s inevitable that at least one of them will be forgotten when I’m totaling up a d20 roll. But with a boon, I set the extra die down next to the d20 and I’m good to go. I might forget why I’ve got the boon if enough other stuff is going on around me, but I’ll still remember to roll it.
Rule of Three
A parallel realization that popped into my head while thinking about how to fix the too-many-bonuses-stacking situation that version 2 of the CORE20 rules had created was that D&D has always had two different types of bonuses. Not in terms of what bonuses apply to, but whether they apply permanently or for a fixed, usually short, period of time. Thinking about that idea some more led me to the understanding that the second category of temporary bonuses can actually be subdivided again, into bonuses that endure for multiple rounds or more, and bonuses (almost always combat focused) that benefit a single roll and then are gone.
So it was that while playing version 3 of the CORE20 alpha playtest, I realized in a fit of inspiration that even though boons and advantage individually weren’t quite what the game needed, using both together could create a flexible mechanic that would streamline the mechanical underpinnings of the game. Version 4 of the alpha playtest thus rolled out the system of benefits that’s at the center of the CORE20 rules today, splitting up the modifiers that can be applied to d20 rolls into three distinct categories, each with a distinct use — bonuses, boons, and advantage.
Bonuses, Boons, and Advantage
Having three categories of potential benefit to juice up your d20 rolls in CORE20 (and, of course, the inverse three categories of potential downside to drag down your rolls) is meant to make it easier to understand what type of benefit you’re dealing with, and to quickly develop an instinctive sense of the tactile mechanics of rolling with banes and rolling with advantage.
Bonuses in CORE20 are fixed. They’re always permanent. When you have a bonus, it sticks with you as long as whatever provides the bonus is with you. Boons (added to CORE20 rules with Rob Schwalb’s generous permission) are short-term benefits that last for a fixed period of time, usually a number of rounds or minutes. Advantage is a one-off benefit that lasts only for a single roll (or in some cases, as with flanking in combat, for a single successful roll).
With boons replacing short-term bonuses, the worry about too many bonuses stacking is gone because you don’t add multiple boons together — you roll them all and use the highest roll. So the more boon dice you have, the greater your odds of rolling the maximum benefit. And as an aside, rolling boons and banes in CORE20 is a great excuse to use your extensive collection of backup dice alongside your main dice, especially as a GM.