Thoughts on creating a Spellcaster that uses hit points for spell casting instead of spell slots.
I was just wondering about home-brewing a walock NPC who’s patron saps hitpoints in exchange for spell casting. Essentially, as long as the character has hitpoints they can cast as many spells as they like but with each one it takes a toll.
Balance is obviously an issue here in preventing them from just being healed by the party and used as a spell battery in exchange for healing but Im thinking perhaps balancing that out by making con saves to prevent them from passing out from blood loss or something from wounds appearing on their body as till for the spells. Aswell as that, spells would have different hit point costs that scale with levels like a first level costing 5, 2nd 10 and so on.
Backstory and lore could be pretty interesting as to how they received their patronage, why they took such a harmful deal, they could be good or evil depending on their motives for doing so and other fun stuff!
Let me know what you think or if you have any ideas!
Warlock is required to cast their spells at the highest level. Since this is a warlock patron it probably shouldn’t be allowed to pick and choose which level of spell it can cast. Consider also converting the warlock spell slots it gives into bonus HP to fit the flavor, but probably at a less than 1:1 ratio for what it costs to cast that same spell since they have innate HP and healing.
As you’ve suspected, this is gamebreakingly powerful and absurdly difficult to balance. Every build in the game would benefit from having this ability and would be made stronger by multiclassing into it. Every other warlock would be pointless because choosing another one would lock you out of this patron. Any multiclass caster is an infinite spell slot source by itself.
You could try to balance it by making it once per day, but why? That’s too fair and not the original intent of design, just accept the imbalance it creates and make it fun to use.