Escape from Castrum Centri bug

I went into the fight and killed one npc. I then clicked the rope on the elvaan npc during the fight. After which I killed the rest of the mobs. Once all the mobs were dead I went to remove the taru's rope (papalymo?), it would go through the motions, but nothing would happen. I tried for about 5 minutes, and eventually logged out and in to reset the quest.

Your objective was to free them first before it switches the objective to kill the imperials. You probably bugged the game by first killing the imperials before freeing both NPCs.