The Steel Guardian (or whatever) who uses fire balls is the toughest of the 4 guardians. He doesn't leave much time for hit-and-run tactics. As a warrior I had to use a few potions, but was able to go toe-to-toe with him. As a survivor/archer on hard, I gave up after a few tries and used a scorpion. You could try the other three first and see if you can go up a level (or at least get some better equipment dropped).
The bodyguard you get from the statue in the room south of where you placed the three orbs to get the portal to the level 2 stairs. He is slow; I left the catacombs deliberately to release him, because he was more trouble than he was worth, IMO.
