Instructions
Change to fourarms and use the tombstone to punch Ghostfreak. This will take Ghostfreak out of his form and allow him to be damaged.
Change to wildvine and pull the cords on the curtains in the battlefield down. Continue pulling the curtains until Ghostfreak falls through the floor.
Change back to fourarms.
Push the forever knight statues so that their shields reflect light onto Ghostfreak.
Attack Ghostfreak. Once the light is reflected onto Ghostfreak from the statues, you will be able to directly attack and injure Ghostfreak. Simply keep hitting him until he is defeated.