Hello i play a mab in Dungeon keeper II, that i made my own.
Dungeon heart with 8 imps around it in the center and four portals in the corners of the structure.
It is single player and has no hero-belongings
Terrain includes rock, indestructable rock, gold-rock, infinite gem rock, water, lava and mana vaults.

I already placed lairs and hatcheries and a library, everything 5x5 squares.

Why still no creatures spawn out of the portals?

Edit: i found it now:
In the list at tzhe left i could open keeler properties and the creature pool was empty. now i filled it and creatures appear.