Ok so how will we resurrect the lamb we all love.

My first idea. Bring prey to an all you can eat buffet. The ancient magic of the endless food may be enough to eventually sate even the hunger prey now has. This will surely allow him to stay permanently as a ghost-thing for crimson, however if we have a bit of luck it may also allow prey to break free from the hunger in death and then come back to life.

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Crimson or Lemon Pink find Discord and convince him that bringing Prey back would be an awesome way to troll Celestia. Discord thinks the idea is hilarious and rips him out of hunger land. Celestia has a heart-attack. Roll credits.

I think there are other ways, either very old or not discovered yet. There are many forms of magic after all.

Poke corpse with stick.

Well, wouldn´t it be possible to "pin" the Prey-Spirit into different kinds of bodies? Simple Posession might be easy to do if you have advanced knowledge of Voodoo, but there could be some gimmick; like the new body must have the size of the old body. And due to friction it would only be a temporary solution. It would explain any off-character scene from the Ponyville Fillies honestly.