Obert's Mushroom Hat

is a very rare drop available for looting from Obert of Bones boss. Cosmetic items are to be used in inventory>character>costume: open inventory, select "character" drop-down menu, select "costume" from the drop-down menu, drag the cosmetic item in the corresponding costume slot.
 * exists as of level 1 and level 7 one, the latter requires character level 7 to wear.