You are deeply mistaken... The Staff with Cloak of Deadly Shadow is:
1) -2 combat spirit and luck for the opponent
2) -20% initiative
3) -1 speed!!!! This is what matters against an Elf!!!
20% initiative on the staff - I'm not saying I'm against the staff
-1 speed won't help, because there are Boots of Speed and Aura of Speed
Added 1 minute ago
The enemy will have a tactic, and probably Retribution. But there might not be true luck.
Added 2 minutes ago
You can try it, but not in an open field. Nimues is best during a siege or defending a Castle... The only question is, how do you lure the Elf?
It seems to me that taking a Castle from such an Elf is suicide.
And regarding the idea that you need to focus on Light magic just to reduce the speed of the Warriors and Nymphs - I think that's a bad idea. We need to come up with something else. By the way, do you know about the Elf tactic of using several Berserkers? That's where a Demon might really be in trouble. In any case, besides Nimues, I don't see any other candidates.
Added 11 minutes agoFroska
Once again: I'm playing hot seat, so opponents will notice what I'm doing, and to put it mildly, I'm doomed :)