An immortal weapon used to bind this demonic entity. It sounds an awful lot like the classic tale of the "master sword" and o.g. Gannon.
But it also fits in with the mysterious arm from BOTW2 that is pinning down what we assume to be malice filled Gannon.
The tribe from this classic pulp fantasy tale also reminds me of the Zonai who share similar stone age or barbarian themes in the little we "know" of them.