On the latest version of 2.53 (Build 33, Release 3, I believe), enemies that use ghost.zh are invisible and do not display their sprites.
^Isle of Rebirth, Hinox miniboss
^ItKotBBG, Beamos enemies (bottom left and right corners)
^ItKotBBG, Wind Wizzrobe enemy
^Umbral Cloud, Ramrock boss