you can always check the compatibility information thread, which ATM is right below this one, to see if the item you're interested in is on it. Almost every item on Gaia that works is on that list. For Fallen Wish, there is one pose that shows from both sides (Way to the Stars) which will be visible when you use an IA invisibility glitch. But it's not a being, it looks more like a pair of wings. You can find out for yourself, for any items you have, just put on Longcat (emgnol) or Will-o-the-Wisp (I am Wisp) and then put on whatever item you're curious about. If it shows, then it'll show when you put on the dander/coffin/jack-o-lantern to make the longcat/wisp disappear.