So first of all thanks to Dallarian for this great guide and everyone who helped with the information. I've been playing battleforge since EA times, but did learn a lot new tricks here.
I want to add two tricks for players struggling with the Nighmare maps. I've beaten both maps on expert solo with them.
1) Nightmare Shard:
In Nightmare Shard the witch spawn group/patrol consists of 1 Twilight Witch, 2 Vilebloods and after a while 2 Twilight Whisperers. There are 4 witch patrols (1 from each camp type?). They spawn alternating at east and west camps. If you don't kill the witch
