If you are the sword x), then you definitely need a host character who will wield you. And basically, all the host's power comes from the sword, meaning that without you, it won't have either your stats or abilities.

So, the host could be another player. What would happen in that case? Whose stats would be used? How? Another option could be various spirit-controlled armor/golems in the sword, but it would also be strange if the difference between better and worse armor for the sword-character was purely visual.

Just don't expect immortality. All items here are destructible, and spirits are ultimately killable.

I'm not entirely sure where these ideas came from. If I wanted immortality, I would play a lich with a thousand spare bodies scattered across a hundred secret laboratories. Or a character with a custom belief who considers himself a god and draws strength from that. However, the latter option could be amusing in itself.