Boon dice are an added option for D&D 5e games, an ability similar to an epic boon (Dungeon Master’s Guide, p. 230) but available to lower-level characters and a bit more versatile. Dungeon Masters should decide when and if a character gains boon dice as an option. It could be a boon all characters are granted as part of the campaign, acquired in exchange for an ability increase or a feat at the appropriate level, or acquired similar to a magic item (up to and including attunement by the character). Boon dice can represent the blessings of certain powers, an innate heroic quality of certain characters, or the ability to draw upon some supernatural power within the context of the campaign setting, to name a few possibilities.
You have a number of “boon dice” equal to your Proficiency Bonus. The size of the dice is determined by your level: They start out as d4s at 1st level, increase to d6s at 5th level, d8s at 11th level, and d10s at 17th level. You regain all expended boon dice after completing a long rest.
For each point of Proficiency Bonus, choose one of the following things you can do with your boon dice. You cannot spend more than one boon die on a single option or roll.
- Roll a boon die and add its value to the result of an attack roll you have just made.
- Roll a boon die and add its value to the result of an ability check you have just made.
- Roll a boon die and add its value to the result of a saving throw you have just made.
- Roll a boon die and add its value to the result of an attack roll, ability check, or saving throw you have just made with a specific ability, chosen when you acquire this option.
- Roll a boon die and add its value to the result of a damage roll you have just made. On a critical hit, you have the option of spending two boon dice to the damage roll (an exception to the normal one die per option rule).
- Spend your bonus action, roll a boon die, and regain that amount of hit points.
- Spend your reaction, roll a boon die, and add the result to your Armor Class against an attack that just hit you or the next attack against you (your choice).
- Spend your reaction, roll a boon die, and reduce the damage you just took by that amount. If the damage is reduced to 0, the attack counts as having missed.
- Spend a boon die to immediately reduce your level of exhaustion (see Appendix A of the Player’s Handbook) by 1 level.
When you gain a level, you can choose a new set of options for things you can do with your boon dice.