if i am using unknown nation, but my opponent plays an enhancement that interupts a card and discards it, can they target unknown nation? had this happen once but i dont remember what the other card was.
If you have already discarded Unknown Nation to use its ability, and you had it activated as a curse on the artifact pile, there is no card currently that could stop it because it in-and-of-itself cannot cause the losing condition, and so it would be out of play before any special initiative would allow you to play a targeted negate/interrupt against it as an evil card. You cannot target cards out of play unless they create a losing condition (see Invoking Terror).
If you hadn't activated it, then they can discard it in any way they would normally be able to as a curse/artifact.
If you used it as an enhancement, and it was the
last enhancement played, and you discarded it from battle, then I believe an Interrupt the Battle could target it.