User blog comment:IamJakuhoRaikoben/Chapter 411: Quid Pro Quo, Review./@comment-110.55.1.170-20141202014343

So Natsu wasn't able to defeat a member of the Kyuukimon + Mard Geer alone, while Gray took out Silver, Tempesta and now finished off Mard Geer. It seems Tartarus arc is more about Gray.