are you sure you killed all 4 minibosses before heading to the last boss? theres 2 on the water side on 2 on fire
otherwise just try to restart the instance? i think the normal mobs dont respawn if you 'fail' and re-enter but not sure about the bosses
look i have killed 4 mini mobs and than it was a problem with internet connection but after i fixed the problemi logged in the game. i was out of pailaka but i reentered and quest continoued from the place where i was "The Final Enemy" so i went there where it should be but it wasn't there.
hmm i lagged out once in that palaika too and when i went back in just went to kill the last of the 4 bosses and then the end boss
have you checked if the other minibosses respawned? otherwise i dont really know, you might have to send in a support ticket :S
Just don't be so curious like i've been :D do not enter the underwater passage b4 killing all bosses until the last one. Otherwise he doesn't appear (dont remember his name). If you fail, better thing is to abandon&retake the quest. I did it this way and it gone well (and i did not enter underwater that time lol!).
please help me i'm on pailaka quest and now i must kill the final mob but it's not spawned
The final boss Adiantum is near the room of Papion. Go back there and dive into the pool under the bridge. The underwater passage, under one of the stairs will lead you to the secret room where is Adiantum. Kill him. RAWR!