This is happened when i was in beggar nest, well i haven't speak to anyone at town, just to a man said that his brother is joining a strange cult, so i followed his direction, finished the cult and somehow through the graveyard i entered the Yuan-Ti nest. This is when the problem start, well since the Yuan-ti is soooo strong, i ran away using stone of recall, then hired a henchman and back again, after that i killed the Yuan-Ti, this is what i mean problem, she's still standing ( just standing, not even move) but the game says that she's aready dead ( there's "dead" label above her) and she also drop nothing..........
then i come back to beggar nest and found out, that there are lot of people i should speak with, including the one involving me in the Water Boys quest, so i finished the Water Boys quest, speak to everyone in the city, and seems like i've done all that could be done, the quest still unfinished in the journal, i also tried to speak with Aribeth, but there is no new option .... and i don't know what to do again....
Oh almost forget, now The Yuan-Ti is laying on the floor, still "dead", nothing else there, no zombie, monster etc anywhere in town.........
