I've played this map a few times but the Lord of the realm will not show up. I've cleared everything out but no luck....not sure what to do. Cannot get past this level

If I recall correctly, the parameters for him showing up are: the other Keeper is defeated, all heroes on the map are currently dead, and you've played for a certain amount of time (a flag timer starts when you start the level).

If you managed to win in a very short time period, you may just have to wait. If that's not it...not sure. Only guess would be some lone hero that you missed somewhere.