You open the door into a 30' x 20' room. Unlike most in the dungeon, this one is lit, with light shining in the center of the 15' high ceiling. The walls here are plastered, and feature ibis heads - sixteen in total, each staring at the center of the room. A thick layer of dust covers the floor, and you spot two sets of small footprints, likely those of a halfling or gnome. One set leads south, out of the room's sole doorless exit, and the other leads west, back the way you came.
On the north wall is a set of bronze double doors, elaborately carved with images of ibises, baboons, human skulls, scrolls, and strange objects you can't identify. The right door contains a large keyhole; based on its size the corresponding key must be very large, at least 8 inches long and an inch thick.