Generally speaking, an artifact is an item possessing some characteristics that make it extremely valuable. Age, religious significance, and military fame are common traits of artifacts in both real life and fantasy worlds.
In IVAN, artifacts are items that have been given a name by their creator(s) and a special magical ability. There are really only three things you can do with artifacts: use them yourself, give them to an ally, or sell them. Choose wisely what you wield, and sell an artifact only if you are desperately in need of money.