The hydras are mean. I've seen it done with two chars:
Char 1: Owns the Crystal Demons using the method above
Char 2: Fires at the hydras from the Crystal Demon room and kills them, then runs down to check the bodies for a key. Use the ticket to escape and return to the crystal demon room if no key drops.
The next room I think can be done with just EVs. The final room was easy: E field the entrance to the room where you start to keep the crystal mummy things away from you, then just kill them with pets or arrows.
