If you are playing on pvp server its good keep Yalahar Quest unfinished and Annihilator room.
Unfinished Yalahar quest let you use Globe which starts last mission of The Quest and noone can enter room then so you can lose there your skull for example.
Many ppl have done Annihilator quest so if you want run away from skulls or not much time left with your skull its good to hide there. But ofc dont go there with 15 min left cuz someone can come there on noob character and keep your PZ. :)