What does Darkness do?

[Taqwus]

One might note that darkness does not appear to impair the use of 100-prec 'always-hit' attacks, like Illithid mindbLasts or Incinerate spells.

[alexti]

Darkness is a "must have" spell for Ermor, but it's nice for other nations too. Ritual-summon undead horder or 2, let a lich lead it (scripted to darkness) and you got a very decent force. And it is also a good way to surrprise the opponent.

[Zen]

Any nation that makes use of Longdead Archers (Reanimate Archers) is best used by this spell as well. Unless you are facing loads of undead, Darkness will allow banishements to veer very far off while your banefire arrows decimate the enemy.