|"That's not what happened at all!"
This topic is considered non-canon because it never appeared in the TV series.
The Bronzed Bone Axe is a Skulkin weapon from a LEGO Ninjago: Masters of Spinjitzu set. It is a simple hatchet-like axe with a bronzed blade and a bone for a handle. It is described as a basic weapon wielded by new Skeleton Warriors, who likely upgrade to the Silver Bone Axe as they gain experience.
Great for hitting and slicing, this easy-to-use blade is the first weapon young skeletons get. Why is it bronzed? Because that’s what proud parents do.