User blog comment:FairyRaven/Fairy Tail Chapter 425: Sabertooth X792, Review and Commentary/@comment-31.132.65.54-20150324135043/@comment-24039250-20150326034733

I'm glad someone states the shadow, since most people just figure Rogue goes evil on his own due to Cat Death. Since the shadow has been aiming at controlling Rogue for most of his life, according to F-Rogue, it's inevitable that he will become evil. Frosch's death, the closest friend he has, was just the trigger that the Shadow has been waiting for so then he can become one with Rogue. He will be in a weak state of mind which will give the Shadow enough time to become one with him.