Ghost Knight

The Ghost Knight is an optional boss in Mother 3. It is found in a single room in Osohe Castle. He is disliked by all other ghosts. A ghost located in front of the Ghost Knight's room will ask the player to defeat him. He is actually a Ghost Armor, but if he is encountered in battle before fighting the other two enemies in the room, the Ghost Sword and Ghost Shield, the three of them will combine into the Ghost Knight.

Battle Memory description
''When the empty-handed armour gets a hold of its sword and shield... terrible things will happen.''