Many years ago I wrote a homebrew magic system for AD&D that centered around the idea of a universal magical force. I realize that this idea might not be 100% original. 🙂 Anyway, spell-casters in this system had a shared hit point and spell point pool… their own life force powered their spells. It actually worked very well and created some interesting opportunities as the players explored other sources of magical energy (force vampires are fun).

I’m still fascinated by the concept and have been thinking about how I might work this into a Sorcerous Origin for the 5e sorcerer class. As a stepping stone to that end, and with dungeonmook’s help, I wrote a cantrip that gives 5e spell-casters an option to dig deep, tapping into their life force to cast beyond their normal abilities. It comes at a hefty price though… so be careful out there.

NOTE: We’ve gone back and forth a number of times tweaking this one… debating the balance between the cost of casting such a spell and the potential benefit. I keep picturing this as a “last ditch” spell, one that you might use when you are out of spell slots and need one last punch to defeat an adversary; even at the cost of your own life. That said, it should be somewhat useful at other times as well. The first version below is closest to the original idea and directly burns hit dice and hit points in exchange for spell slots. The second taps into the exhaustion framework in the PHB to simulate the drain on the spell-caster’s body. Which one do you like better?

 

Cannibalize I

Transmutation cantrip
In the Cleric, Druid, Sorcerer, and Warlock class spell lists.

Casting Time: 1 bonus action
Range: Self
Components: V, S
Duration: Instantaneous

You tap into the very life force that keeps your heart pumping to power your next spell, sacrificing hit dice and hit points to regain a spent spell slot. When you cast Cannibalize choose how many hit dice you will sacrifice up to your current hit die count. You regain one spell slot equal in level to the number of hit dice you choose to expend. You can only regain a used spell slot and cannot gain a spell slot that you would not normally have.

When you use the regained spell slot, you gain advantage on one spell attack roll (or you can impose disadvantage on one targets’ saving throw against the spell). The regained spell slot is usable until the end of your current turn, at which time it expires.

At the end of your current turn, as an additional cost to casting Cannibalize, roll each expended hit die and you lose hit points equal to the result.

 

Cannibalize II

Transmutation cantrip
In the Cleric, Druid, Sorcerer, and Warlock class spell lists.

Casting Time: 1 bonus action
Range: Self
Components: V, S
Duration: Instantaneous

You tap into the very life force that keeps your heart pumping to power your next spell, pushing yourself to the limit to regain a spent spell slot. When you cast Cannibalize you regain one spell slot. You can only regain a used spell slot and cannot gain a spell slot of a level that you would not normally have.

When you use the regained spell slot, you gain advantage on one spell attack roll (or you can impose disadvantage on one targets’ saving throw against the spell). The regained spell slot is usable until the end of your current turn, at which time it expires.

At the end of your current turn, as an additional cost to casting Cannibalize, you suffer from exhaustion as determined by the level of spell slot regained.

Spell Slot Level Regained	Effect (as per PHB 291)
1	1 level of exhaustion
2	1 level of exhaustion
3	2 levels of exhaustion
4	2 levels of exhaustion
5	3 levels of exhaustion
6	3 levels of exhaustion
7	4 levels of exhaustion
8	5 levels of exhaustion
9	6 levels of exhaustion