When you /kill an elder guardian ghost, you would see the name of it is untranslated. If you do the command /give @p spawn_egg 1 120 it will give you an item named “item.spawn_egg.entity.elder_guardian_ghost.name”. It should be, based on other spawn egg names, “Spawn Elder Guardian Ghost”. Please fix this. Also, the spawn egg has a model but no texture, so it is plain black.