My question is what's the deal with Kiatha the Archer in Blackthorns Castle? An invulnerable(yellow named) npc that can attack? What's the deal with that?
Back in October last year, towns were attacked by Minax's 'captains' -
http://uo2.stratics.com/posts/42488
In game fiction, the ending of those invasions came when Blackthorn magically redirected the invaders into copies of pieces of the towns they attacked, those town segments are in his new dungeon and the magical barriers prevent the invasion troops escaping the area.
Fighting the 'dungeon versions' is pretty similar to fighting the originals invasion, but with less space to manoeuvre - kill off the lesser stuff to make the Captains vulnerable, kill Captains to make the beacon vulnerable. I seem to remember it takes three 'waves' of attacks to desroy the beacon - after each 'wave' you destroy, it becomes vulnerable for a short time (I think it's actually for 'as long as it takes for people to do 1/3 of it's HP in damage?), then it resets to invulnerable and the next wave of attacks begins soon after. The dungeon invasions rotate randomly around the small city areas, once one is totally defeated and the beacon there destroyed, a new one will come along in a few minutes.