Andel Crodo submitted this

All the monsters are available to me now and I've been having trouble keeping everyone happy. Spiders don't like Flies, Bile Demons don't like Skeletons, Vamps don't like Warlocks, etc.

It's a matter of planning out your dungeon beforehand. Build a huge training room at the center of your complex and plan to place a door at two opposing walls in it. On one side, place lairs and a hatchery for Bile Demons, Warlocks, and Spiders, let's say, and on the other side of the training room, place lairs for the other monsters as well as a hatchery for them too. If a creature is stubborn and makes his way into the wrong lair, sell the tile it makes, physically pick it up, drop it inside the other lair, and lock the door until it makes it's lair in the room you want it to be in. The doors also come in handy for locking all the creatures out when your gold reserves are running low.

Note that all these opposing creatures will train and not fight each other even though they are in the same room. They will exit through the appropriate door to their lair and will never attack one another unless you physically place them near each other. Be warned that after battles, they may fight on the trip back to their lair too (but not always), so keep an eye on them.

But there's more, scavenger also submitted his thoughts on this subject!