Someday I would like to run an old school D&D game that uses hit dice as an expendable resource. Here’s how I might do it.
The Basics: You have a reserve of as many hit dice as your level, and your hit die size is based on class (d4 wizard, d6 thief, d8 cleric, d10 fighter). You can spend a hit die on a variety of different things, and you refresh your supply when you rest long enough to make you wonder if maybe it’s not safe to rest again (e.g., long enough to trigger a random encounter).
Injury: When you fall to 0 HP or less, roll your hit die to determine your fate. You don’t lose that die from your reserve, but you can opt spend as many additional dice from your reserve as you want and take the highest result.
1 = dead
2 = permanent injury and incapacitated at 1 HP
3 = temporary injury and incapacitated at 1 HP
4+ = temporary injury but still on your feet at 1 HP
Every class has access to this option. Each class has some additional options for how to spend hit dice from their reserve, as well. Unless otherwise specified, you can roll any number of HD at once and use the sum for these abilities.
Second Wind: As an action, and regain HP equal to the sum of HD rolled.
Cleave: On successful attack, roll HD and apply the results as damage to the same or adjacent targets. Indicate which die goes to whom. (If playing a game like Into the Odd, where the attack roll is the damage roll, replace this with: Roll any number of HD for additional attacks on your turn.)
Maneuver: Roll before or after attacking, and add the sum to your attack roll. If the resulting attack roll exceeds the target’s AC by 5+ (or comparable defensive score by an approximately appropriate degree), inflict a condition or affect the target’s position (knocking down, pushing back, etc.).
Spellcasting: Whenever you cast a spell, roll HD. If the result is over the spell’s level, the spell goes off without a hitch, and can be cast again. If the result is on or below the spell’s level, you lose ability to cast it again today, or you experience catastrophic magical side effects. (Higher level spells thus require multiple dice for a chance to avoid risks.)
Metamagic: Add the HD roll to a spell’s damage, number or combined levels of targets, range in “squares” or yards, or duration in the unit of time already specified by the spell (for anything except immediate effects without a duration).
Counterspell: Deflect or disenchant a spell. If your HD roll is on or under the target spell’s level, you experience catastrophic magical side effects or suffer the difference in damage (your call).
Finesse: Roll any number of HD once after a failed save or ability check, adding the result to your roll. Describe how you correct your course at the last moment.
Backstab: Add your HD roll + your level to damage done to an opponent unaware of your presence. Whenever you roll a 6 on a backstab, roll another d6 (not from your reserve) and add that to the total.
Shift: Spend to move an as many yards or “squares” as your HD roll, either quickly, carefully, or silently (choose 1).
Lay on Hands: Touch a wounded target and roll HD. If they are worthy in the eyes of your deity, they regain as many HP as your roll.
Turn Abominations: Drive back creatures considered abominations in the eyes of your deity, making them unwilling to come within spitting distance of you. Only creatures with HD lower than your roll are affected (e.g., you need a sum of 4 to turn a group of 3 HD creatures). After they take as many turns as the highest die in your HD roll, they can attempt a save to break the effect on their turn.
Miracles: Works like wizard’s spellcasting, but uses the cleric spell list (or the same spell list, but limited to keywords relevant to your deity). If your hit dice don’t exceed the spell level, rather than a magical mishap, you take the difference in damage (unable to safely channel your deity’s power), or lose the ability to cast the spell for the rest of the day (as your deity protects you from yourself).
I fixed what I believed to be some errors from the first time I posted this months ago, but I still haven’t playtested it yet. If you ever give it a try, please let me know!
This post originally appeared in an earlier form as “Hit dice should be as exciting as they sound” on Google+ on May 29, 2018.