The Great Ravine

On the Eastern side of the Southern Plains there is a giant ravine. It was carved by the Great Beast that lives under the Blue Desert. Observant PCs will be able to tell the ravine was not made by natural means. If it is followed to its end the ravine suddenly turns straight down into the ground, becoming a massive hole that goes down for miles. Eventually the hole levels off and leads to where the Great Beast lives. Players who try this anytime soon will die because the great beast is going to be at least CR 20.