Nameless Seer spawned outside reachable zone in conqueror arena

I was confused because I had reached 0 monsters remaining and the Seer didn't pop up before I went into the arena but then there were some extra mobs in the arena which ended up spawning the Seer. Unfortunately after the fight the arena shrunk and I was no longer able to walk far enough to interact with the Seer.



You can kinda see him in the lower left and he's visible on the minimap.