Amaterasu

Amaterasu produces black flames at the focal point of the user's vision. In most situations, this makes Amaterasu impossible to avoid. However, if the target can move fast enough to prevent being focused on, Amaterasu will miss them when it's cast. The target must make a Dexterity saving throw DC(25 )or take 20d8 fire damage and ignores fire immunity. The caster can use his bonus action to have the flames follow the target, the flames have a 60ft movement speed. When the flames hit the target redo the dex save. Casting this spell gives the user 1 level of exhaustion per casting.