Your goal is to find Urgon's part. To reach it, you must go though all of the 4 buildings.
When you first face the monster, immediately run into the building to your left, climb the ice ledge there inside and run up the ramp. On top of the ramp there is a block which you must pull out of the wall, then slide down another ramp.
Now run into the opposite building where you find a wooden ramp. Climb it, run up the ramp (it will collapse).
If you continue this way you'll find the secret chamber where Urgon's part is hidden.