User blog comment:Omega natsu2/Fairy Tail Zero: Fairies in Your Heart, Review./@comment-4449950-20140718051211/@comment-7418318-20140718084537

Hmm... maybe Precht lost his eye and originally the Demon Eye was just a replacement. Maybe he was tricked into believing that it was either harmless to use a Demon's eye or that it wasn't one in the first place and it was this eye that corrupted him slowly.