Yep. You needed imps to dig out rooms, reinforce walls, and carry corpses (turned into zombies or something in the graveyard room) and loot (used to pay of your other monsters and cast spells, iirc) back to your dungeon.

You could do things like pick up imps to make them prioritize a task, or slap them to make the work faster (took a slice of health out of them though).