Can you remember your winning conditions?
If you checked "allied win", you need to get everyone (last mage in that case) to your allies. If you not, but checked "elimination" win, then you must eliminate
everyone, neutral included.
If you excluded both... well, then there are a lot to check.
I hope, it can be checked inside game, but I never did it.
Other planes are packed with very-high level monsters and all are tiny. So it's way to get a lot of experience and loot in short time, but hard to do.