The creature is now quite thoroughly dead and splattered across the floor, thanks to the additional blows. It remains quite clearly dead, and no further threats appear. The room is 30' by 40', and has no other exits than the one you came in by. It appears the creature had hollowed out part of the sarcophagus to use as a nest. There is nothing of note in the room other than the sarcophagus and the corpse of the creature.
(PS: I already rolled knowledges at the start of the battle; better to not know whether you should know or not, i.e. I prefer to keep the knowledge roll secret)