The tooltip just says that it will return to owner when thrown, but it will also automatically equip itself regardless of whether or not it was equipped when thrown. This doesn't use an action point but the game treats it as an action, so when coupled with The Deathstalker Mantle from the Dark Urge rewards, it removes the invisibility on kill bonus. If this could be made to return to inventory instead of auto-equipping, it would be so much more useful.