Elemental Aura (3.5e Feat)
From D&D Wiki
Elemental Aura [Celestial, Fiend]
Your close relationship with primal elemental forces has manifested in a damaging aura.
Prerequisite: Character level 7, must have a subtype granting immunity to a form of elemental damage.
Benefit: Choose one of your elemental subtypes granting immunity to a form of elemental damage. You radiate a damaging aura that does 4d6 of elemental damage of that type to any creature within 10’ of you at the beginning of your turn.