Atha's Rageful Syphon

For the duration, your Unarmed Strikes, Spell Attacks, and Weapon Attacks deal an additional 2d8 Fire damage and 2d8 Necrotic damage on a hit. If a creature takes the Fire damage dealt by this spell, you gain temporary hit points equal to the damage dealt. If a creature takes the Necrotic damage dealt by this spell, it cannot regain Hit Points until the start of your next turn.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the fire or necrotic damage (your choice) increases by 1d8 for each slot level above 4th.