I agree a pure ogre city is very unlikely. A mixed city with many different races is what I expect. Ogre Lord could be a tier 2 ogre evolution. If Richter is unlucky the city is built on top of a place of power and the Ogre Lord not only holds the crystal but managed to use it for his tier-up achieving a special race like mist lord giving him massively increased power within his domain. That would certainly explain him holding power for an extended period.