I wait to clear out that castle until after I have obtained blasters.The easiest way to do that then (without magic) is to:
1. Turn the cube read
2. Make a run for it to the area where the cube is
3. Fight the orcs there and touch the cube
4. Make a run for the long ramp going up to the balcony.
5. Run down to the secret area where the Armageddon books are
6. Jump over the balcony railing and run around the corner
7. Grab the memory crystal, touch the wall plaque there
8. Touch the now red cube there and portal into the "book" room
9. Destroy the book of Liches
10.Portal back to Kriegspire town
Works for me every time. After I get blasters, I go back there and wipe them all out.