For all the long description detailing the path required, the next outpost is only a short walk away. Speak to the Guard of the Isles near the eastern gate. He will let you pass to the other side of the gate, (if you do not have the quest on your quest log, he will refuse to talk to you). Follow the winding Forbidden Path and enjoy the beautiful scenery along the way. The crevasse in the cliff can be rather well hidden if you don't look hard enough, but just follow the instructions given by Rioka.