Erinys held onto William, and supported his body, as blood seeped from almost every pore of his body.
When the Half-ling suddenly appeared in front of him, the red-headed teenager forcefully canceled his attack. This caused a backlash, which created severe internal injuries.
Truth be told, William had almost lost his senses when he initiated his final attack against Thanatos.
The blood inside him boiled as if it was set on fire, urging him to thrust his sword on the God of Death's chest, piercing his divine heart, and obliterating it to pieces.
However, after seeing Erinys stand in his way, he regained his sanity and forcefully canceled the blow that was meant to kill Thanatos while his Godslaying powers suppressed his Divinity.
Just like Superm*n being weak to Krypton*te, Gods were inherently weak against God Slayers. It was similar to the hunter and the prey. Both were natural enemies, with the God Slayer overcoming all adversities, killing the God he was fighting against.