The Castle Stronghold's Treasury is much like the Tower Armory in terms of twisting corridors, but it's more fancy and just as rich-looking as the treasures within. Heroes shouldn't let the opulence fool them, however; it's protected from would-be thieves by traps, secret switches, and animated armor. The treasures in the Treasury is hidden by many secret doors and switches, but they're easily found by an observant hero. Completing this area leads to the Chimera's Keep.
The Ice Axe of Untar is found here, but requires a hitting a sequence of switches in the Treasury to obtain. The last switch is outside of the Treasury proper, and along the path to the exit. The Scroll nearby will alert a hero when the axe is available. There's also a Treasure Room here (Space) that unlocks the Jackal.