With Kayn/Rhaast release, we got some new insight on the Darkin, however...
... Are the darkin actually all weapons, all 5 of them? If that's the case, who created them? Who gave them sentience?
Or were they powerful living creatures, that, due to their immense power, got sealed on weapons? If that's the case, who sealed them?
Or is Rhaast and the darkin residing in Varus' bow special cases? What if Aatrox managed to avoid getting sealed, maintaining is original body? If Aatrox was indeed sealed/or was always the sword to begin with, who was the possessed human?
What do you think?