Taldaline's Aurora

You fill the sky in an area up to 1 mile square with bright ethereal lights.

When you cast this spell,  you may choose any from the following creature list: Abomination, Celestial, Fey, Fiend, Elemental or Undead.

Creatures of the chosen type(s) suffer  disadvantage on all ability checks and savings throws while under the sky's effects. Only full cover prevents this from taking effect.