What did I just buy?

[olikara]

Tim,
Yes, that is exactly what it is.

Jim,
You may be right in the sense that this object is not a functional weapon.

Attached find a photo of Kartikeya. He is invariably shown with this weapon rather than Shiva (Since the past couple of centuries, atleast).

Various parts of India represent deities in different ways and the weapons they carry also vary with region and era. Shiva was earlier (1st Millenium) shown with a different weapon but he has now changed his weapon of choice to a Trident

Shiva is nowadays (and usually in the past) shown with 4 essential things:
1. Trident
2. Small Drum
3. A Snake around his neck.
4. Water flowing out of his hairlocks.

I think there is a possibility of it being an appendage to a Hindu Idol (Shiva as Tim showed or more probably his son, Kartikeya also called Murugan in South India) who is more often than Shiva depicted with this sort of a weapon.

It may be a possibility that this item was separated from some Hindu Idol, why we do not know, and found it's way into eBay. The length of the weapon may also be an indicator of this.

But then, this is only my conjecture.