Corillionn can be found in the Catacombs of Shame. Follow the path towards the arena/bull area, but instead there is a corridor to your right in the main area. Go to Small Hallway [67326] and you'll see "Double-paneled service doors provide egress." Enter the doors to be teleported to A Desolate Marketplace. Follow the path around and you'll find one door leads to The Locksmith's Office [67321].
This is a quest master that appears to give "picnic style" randomly generated quests. They provide AP upon completion.