
I can't believe I only just noticed this after like 20 playthroughs.
The fingerslayer blade is like an unfinished, malformed version of the Sacred Relic Sword- both born from the corpse of a God. An unknown one in the case of the Nox, and Radagon/Marika in the case of the sacred Relic Sword.
It seems so obvious looking at them side by side but I never put it together untily first sorcery focused run. This game is so cool.