Boon of Energy Investment

You attune to the elemental energies of the universe. When casting a spell that deals fire, thunder, lightning or cold damage you can change its damage type to another of those types. In addition when taking this boon you gain restanince(And take immunity if they already have the resistance) to one of those types.
Your body takes on properties that correspond thematically to that element, altering your appearance. Additionally any energy around you seems more volatile, fires crackles louder and brighter, wind blows more fiercely, etc.