Where to Find the Mandate Encampment Outer Gate Key in Phantom Blade Zero

In Phantom Blade Zero, the Mandate Encampment Outer Gate Key lies on a corpse in the room below the well in Gu Wangyue's arena, in the west of the Pangzhen region visited in the game's second chapter. Defeating the Chinese opera singer boss and climbing the ladder ahead leads to the key, which unlocks an entire otherwise inaccessible region; the gate itself is first seen on arrival at the Village of Lu.