blindness is cause by a spell that is casted by an orc apprentice and that
thing stops it...
I set up at p1100 x p220 and killed every mob that came within spell range. after 6 hours I had seen Tisella twice and the nightmare once ( then I left). Tisella spawned close by - just north east - but the nightmare popped far north east up by lavaspinners lair. I believe the phs for these mobs are the pathers like Brognot and Sir Lindeal