When you first meet Keldorn in the sewers he is fighting a single zombie near the entrance to the lower levels. There is a bug or glitch if you leave the sewers before actually meeting him and return at a later date.
As you can see in the screenshot the zombies have multiplied. He will kill only one zombie however before initiating a conversation with you. The remaining zombies are just standing around doing nothing.
It happens only when you level up a bit before returning to meet him. My guess is that it has something to do with the different Keldorn versions (Keldorn8, Keldorn10, ...) the game is creating each time you enter the sewers to match your level.