One of several giant armoredknights found in the game. Even though he can be easily defeated by conventional means, his purpose in the game is a bit different. The intended way to defeat him is to force him off the ledge he's initially standing upon by making him retreat a little every time he's struck.
Once he falls over, the Gate Guarder will tumble down the slopes in the room and crash into a boulder blocking an entrance at the bottom, destroying both it and the armor. This allows Juste to access the first Merchant's shop in the next room. After this enemy has been used to break down the wall blocking the Merchant's room, it won't reappear until a new playthrough has been started.