The air becomes nearly unbearable, the stench of rotting flesh growing stronger with every step. You manage to deal with it, though, and sneak your way down the stairs, carefully placing your feet, keeping your balance on the slippery surface.
Shortly after you start to round the turn, you can see them. They are wandering about the room, directionless for now, but they seem more purposeful than those above. 7 or 8 of them just wander about the room, confined by the trickiness of climbing the stairs, and gates at each of the three remaining paths out of the room. The squeaking from before clearly came from unoiled hinges as zombies bumped into the gates.
The only light in the room comes from a lantern resting atop the stone sarcophagus that sits at room's center, its lid cracked, zombies bumping into it now and again.
SpoilerFort save vs retching: (1d20+4)[16]