User blog comment:Collbrande-Ex-Caliburn/Hyoudou Issei's Peerage composition hopes/dreams/hypothesis/@comment-26821288-20161228004608/@comment-9595671-20170128081334

If Thanatos is in the DxD world, then he's probably just another of Hades' Grim Reapers, most likely the original reaper too, than an actual God like he's supposed to be.

The reason I say this is cause I've done some research, and it seems that Hades' stronger reapers Pluto and Orcus are (or were in Orcus' case if I'm reading the info right) his Roman counterparts.