I think that it should take away half of your remaining hp on hit, unless you would normally take more than half of the damage on hit, in which case the higher damage would override the effect. That way it's a bit more forgiving and doesn't just turn you into a worse lost on pickup unless you have extra lives

I would suggest instead of it killing you, it will drain your hp to half a heart slowly instead.

Well I'm pretty sure most people don't download mods when they have no idea what they do, but if you don't care about that fair enough.

Yes, it has EID support for a reason.

So you die upon getting hit and the item disappears on hit as well? Does having it do anything?