Arcane Exasperation

 While spell slots represent an amount of spells that can be cast safely and consistently, some casters push themselves to their limits, physically expending themselves for the sake of magic. These people practice the technique of Arcane Exasperation.

When casting a spell of 1st level or higher, you may choose not to expend a spell or pact slot. Instead, you may choose to spend a number of hit dice equal to the spell’s level and cast the spell. Once the spell is cast, roll the hit dice spent in casting, and suffer the sum rolled as necrotic damage, which can’t be reduced in any way.

This is not my original content, this is ripped heavily from another DM in my community, Mr. Raatz.