Looking for a way to darken magic in your fifth edition Dungeons & Dragons games? Then have I got the perfect homebrew rule for you — Blood Magic!
When you cast a spell, you must expend one hit die for each level of the spell you are casting. In a single casting, you can expend up to a number of hit dice equal to half your spellcasting level.
You may spend additional hit dice (up to 9 total hit dice) in order to cast spells you know at higher levels, beyond half your level (rounded down). For every level beyond half your level that you cast a spell, you must roll the hit dice beyond half your level. The result of this roll equals the amount of necrotic damage you take, immediately after casting the spell. This necrotic damage is called Mana Burn, and it ignores resistance and immunity to necrotic damage.
Additionally, you can cast spells, even after you are out of hit dice to expend. However, each time you cast a spell in this way, you must roll the expended hit dice, incurring Mana Burn damage equal to the result.
If you reach 0 hit points as a result of Mana Burn damage, you gain one level of exhaustion. Mana Burn can kill you outright.
Why use this instead of spell slots?
Spell slots always felt… superficial to me. Despite my favor for the spell point system, I even feel like that feels flat. Even mana points in other systems all feel… artificial?
Here’s the thing: spell points, mana points, spell slots, whatever you want to call them — they all feel made-up. I don’t mean made-up in the same sense as everything in our games is made-up. And I don’t mean like, in the context of fantasy as a genre. What I mean is, quantifying the limits of a spellcaster’s power with something so concrete as spell slots or a point system feels like a bit of a cop-out. It’s not evocative.
I’m fully aware the hit dice system of blood magic is every bit as made-up as anything in fifth edition Dungeons & Dragons. However, because hit dice are tied to health recovery, it feels more flavorful and seeds a certain tone into the world through consequences. Suddenly, magic means something more than just “spend a spell slot, do a thing.” Casting a spell has weight in this system. It has consequences, and those consequences can be dire.
Not only is this somewhat more limiting for casters, but this system also frees casters.
Upcast your spells — if you’re willing to pay
This system gives casters a new moral dilemma: blood for power. Talk about conflict! That’s interesting! It also seeds why people might not trust magic. It gives new weight to high-level casters, and it lets the spellcaster be truly epic in a pinch, but at a cost, both physically and morally.
When you bring different potential power sources, like clerics’ divine casting and druids’ primal casting, it adds new flavor and insight into the world at large. Just imagine, your god grants you miracles… if you pay the toll. You can tap into the powers of the natural world, but in order to preserve balance, you must sacrifice your own well being.
I truly think this variant rule for magic offers new, fascinating development for full spellcasting classes.
What do you think?
Do you like this homebrew blood magic mechanic for D&D magic? Are you prepared to shed your hit dice in health to wield magical might? Do you have thoughts about spellcasters and how to make spellcasting feel more integrated into the world? Let us know in the comments!