Ephemeral is an item property found on Covetous Void Pool reward artifacts. Items with this property lose one point of their maximum durability every six minutes when the item is used while attacking a creature. In other words, players can use these items for a total of 25 hours (6 minutes x 250 maximum durability) while actively fighting against a creature and not just simply being in war mode or the target of aggression. As noted by Phoenix, "the intent is for ephemerals to last for 25 hours of actual fighting time without having to worry about keeping them repaired". Note that the items with this property cannot be fortified and so can never have their maximum durability increased.