User blog comment:IamJakuhoRaikoben/Chapter 452: The Prelude to the Final Battle, Review./@comment-1359064-20150914102551/@comment-1776824-20150914213901

I'm more inclined to believe Invel is a Dragon Slayer, not a God Slayer. Part of the reason Zeref has amassed these forces is to take on Acnologia, and a Dragon Slayer would definitely give him a boost. But at the very least, Invel has to be a Slayer mage, as if he wasn't, then Gray would just be able to devour all of his ice attacks and the fight would mean nothing. There has to be some kind of clash.