User blog comment:B214/Shin DxD 1 discussion/@comment-26709288-20180814233035/@comment-28884330-20180817010312

Unnecessary? Sirzechs is a Super Devil who is Heavenly Dragon-class or perhaps even superior, and he still needed two pieces for MacGregor and for Okita, and a Mutation Piece for Surtr Second. Mutation pieces would be immensely useful to Issei to reincarnate strong people.