Corrinthia's Divine Halo

Upon casting this spell, a halo of radiant light emanates from your head, shedding bright light in a 20-foot radius and dim light for an additional 40 feet. For the duration of the spell, you gain the following benefits:

Radiant and Fire Resistance: You gain resistance to radiant and fire damage.

Damage to Undead: When you first cast the spell, any undead creature within the bright light's radius and can see your halo takes 1d10 radiant damage. 

At Higher Levels:

When you cast this spell using a spell slot of 4th level or higher, the damage to undead increases by 1d10 for each slot level above 3rd.