History and orbs of Dysphoria

Can i eat it?

sure you can but, why? I personally wouldn't do that

Can you cure it with a cleric?

A sucessful greater restoration can bring anyone from phase 2 and 3 to phase 1

Can oreck cure it?

A lot of people other than oreck can cure it, by dealing psychic damage to the creature to certain point, you will bring it back to phase 1 if its not too late. However this method is slower than the cleric. This pool of hp grows with every snapping back to phase 1