User blog comment:FairyRaven/Fairy Tail Chapter 416: Tartarus Arc: Final Part, Review and Commentary/@comment-125.212.122.184-20150119222742/@comment-7418318-20150120093823

That's it! Frog is also a part of END!

Natsu was so surprised and didn't tell anyone because noone would believe that harmless and cute little froggy could be something demonic and evil, but Frog is killed, his part of the power will enter Natsu and unseal him. :P