Mmmmm they might be Hemalurgical spikes (it seems likely given the name) but they would have to grant the ability to store/tap Identity, rather than remove Identity from people. Removing Identity would require the spike be used on them to rip out a part of their spiritweb, which would likely kill them. Unless that's what you meant, and I misunderstood?
And yeah, nicrosil definitely shouldn't work that way, and yet it does. I have no good theories on this, so looking forward to The Lost Metal!