Hey thank you for playing! It is my bad. I didn't test the situation when player jumps out of map in boss arena.
Mob is spawned right there in sight and player cannot outrun it, it is desired XD. Only one route is to pick up the last shard at the library, then the mob will go upstairs, then player can jump on the ground run to the rune. In the boss arena player gets one chance to escape (click E crazy) if player is caught by mob. lol
but I really appreciate to your feedback and the point I missed. ;)