The slope steepens quickly until it can properly be called a cliff. If Sir Walter and Jon the Green are to take the straight path, they must climb. The closest and safest way, without taking a detour, is done in three stages. The first ledge is a mere 20 feet down. The second is 30. The last is a sheer drop 50 feet down.

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Climb DC 10, 15, and 25
with rope DC 5, 10, and 15, but the rope is not retrievable from the last stage unless you have a special trick up your sleeve.
Falls hurt 1d6/10ft, but worse than that they require a Reflex DC15 save or you go tumbling down the next stage as well.