The chamber is partially flooded by a bubbling, putrid lake. A narrow stone causeway carved out of solid rock, about halfway up the wall, is the only way across to the exit on the opposite side of the room.
There is also a narrow stone stair carved into wall leading down to the shore of the lake. There does not appear to be any exits from the lake level however.
On the shores of the lake what looks like an alchemy lab has been set up. Beakers bubble greenish liquid from one cauldron to another, eventually emptying into the lake.
Crouched over the alchemy lab is the same skeletal figure you remember seeing from outside the mine. His huge golem stands silently to the side as the figure carefully sprinkles the contents of a vial into the briny lake, cackling to himself as he does so.