World Master (5e Feat)
From D&D Wiki
Prerequisites: The ability to cast at least one spell and Caster level 15 or higher
You put yourself in danger in an attempt to increase the power of your spells. Spellcasters may use this feat to cast spells with more power in exchange for possibly damaging themselves.
- Roll a d6. On a 1-3, the caster takes a quarter of the spell's damage dealt. On a 4-6 the caster takes half the spell's damage dealt.
- Spells cast above their lowest level double the damage the spell's caster takes, and do not last longer or cost any more time to cast.
For example, acid splash deals 1d6 normally but instead would do 2d6.