Outside the Darklands Mountains sits a sign that reads:
BEWARE! NEAR-CERTAIN DEATH LIES BEYOND! There is an additional note: This area is not even remotely fair. But if you can prevail, it can be greatly rewarding. Be wary. Be careful. Do not go in alone. --Arkham
To navigate around this area, you need to climb up cliff faces. Falling does about 200+ damage.