DiceVR
quite frankly, i might be a bit paranoid with this guess but...do you think the devil wanted eiro to eat his clone? I'm not quite sure what powers exactly the devil has, but considering his forte is manipulation, I wouldn't be surprised if everything the devil said was to make eiro go to a certain conclusion...
So, hear me out. With that demon descendant, the Devil sent Eiro his flesh. And with this blood summoning, the Devil sent Eiro his mana. Is this some long term resurrection scheme? Or maybe something to do with the World, since the Devil knows Eiro has it? Maybe the Devil thinks that if Eiro absorbs enough of him, he’ll be able to use his manipulation powers to take over instead?