The go-zu oni magically polymorphs into a Small or Medium humanoid or beast, into a Large giant, or back into its true form. Other than its size, its statistics are the same in each form. The only equipment that is transformed is its greataxe, which shrinks so that it can be wielded in humanoid form. If the oni magus dies, it reverts to its true form, and its greatsword reverts to its normal size.