It's called Darkness (Alteration 6) or Utterdark (Alteration 9, always in effect). It makes everyone blind which really hampers fighting. Undead are immune.

Another that affects the sky is Solar Brilliance (Enchantment 7) that kills undead by the truckload and blinds enemies.

There is another one that turns the sky pinkish. I think it's Heat from Hell. The Ark casts it too.

[ January 15, 2004, 09:59: Message edited by: Zen ]