You are supposed to drink from the cups to get the power orbs, but I cannot find any cups anywhere. Where are the cups? Behind the see through doors? Cannot bash the doors down. Am I missing something?

Yes.

Behind one of the see-through doors in the hall with the "what will the mighty moose be?" riddle is another door that leads to the hall with the deadly cups which you have to drink.

Probably your characters are not strong enough yet to bash the doors.
If you have quaatloo coins left, visit the dungeon with the casino (Stronghold Slithering Cult, I believe) and use the coins to boost the strength of your first 2 characters.
If that still is not enough, you might try Wizard's Eye to find the correct door and Teleport or Etherealize to get through. Or visit magic fountains which increase Strength temporarily.

It is also advisable to have resurrect, raise dead and stone to flesh spells ready in the Cathedral of Carnage [the name is NOT Cavern of Carnage].

Cathedral of Carnage, that's what I meant. My guys are level 11 and 12. So at least I know now that you can bash in the doors. I don't have resurrect, raise dead and stone to flesh spells yet, though I do have a stone to flesh box. Nor do I have Teleport or Etherealize yet. Hah I just got Town Portal!