The Jungle Scamp

At the mountainous region's periphery, Julien and his party located a monster lurking about. 

It was a bipedal monster with sharp horns, being the size of a giant gorilla but having a slim and agile body. 

This monster was currently resting in a cave and to trigger the hidden quest, one would need to make it notice them.

"Careful. This notorious monster retreats the moment it feels threatened. It'll only attack if it feels it can harm its opponent." Celeste warned. "If you cause it to retreat, the quest will fail and won't trigger again."

This was the reason why it was still uncleared. 

Whenever high ranking Players approached this monster, it would run away and won't show itself, making them fail the quest. 

Once the quest failed, the Players saw no reason to give chase and kill this monster. 

As for the low ranking ones, many died at the hands of this monster and failed the quest by default.