Recently I saw a bug where if in a duel between an Assassin and a Hunter it is possible to spawn a hostile monster in Varlone. Assassin uses Shadow Dungeon and during the Duration the Hunter summons his pet. I am not 100% sure if this is the correct way the bug works because at a point 3 or 2 were spawned at the same time. A bug is a bug and a threat to lower level players in a safe location is still an exploit.