The Flenser, the guards with the boys, the monks, the Dog Master, perhaps the dogs, the entrance guards and the one guy in the front who is patrolling.
You probably could as well force a fight with the partol in the camp.
Mido & flower is also always good to some exp and to get shown another way in, using teleport gloves. But fighting the could be a bit hard.
Not sure, but I think we left the prison before leve 4, leaving the prison gives some very nice exp and also there are few low forced enemies outside. We are currently exploring most of the island, while many Magister in the fort are still alive.
Of course we didn't pretend to be total new to the game.