Arlon is a member of the Forces of Nature, under the command of Viridi. Viridi commanded Arlon to protect the Luna Sanctum from the anyone from entering the Sanctum and releasing the Chaos Kin. Pit processed to the Luna Sanctum without any knowledge of the Chaos Kin. Eventually, Pit eached the location where Arlon is and processed to fight Arlon.
Arlon himself has the ability to obscure Pit's view by darkening his surroundings and shoot at him while in dim lighting. Pit must attack in the direction of Arlon's shots in order to defeat him or wait until the darkness is lifted. Eventually, Pit managed to defeat Arlon, along with destroying the Luna Sanctum.