User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-73.46.6.122-20150727181231/@comment-79.175.64.126-20150728181349

Of all clans, Gremory have highest demonic power and control over demonic powers. Sirzech is irregular since he inherited both Bael and Gremory traits. Rias inherited only Bael trait. Volume 21 will be Vali's volume and focus on 2 heavenly dragons.