"An Engram with a predestined outcome. It will contain a new Exotic if anyone remain to be collected."
— In-game description.
A Fated Engram, sometimes also called an Isochronal Engram, is an Exotic Engram bought from Xûr in Destiny 2. It costs 97 Legendary Shards and gives the player an Exotic or an Exotic Armor piece that is yet to be found. If all Exotics are owned on the players current class, it will instead give a randomly-rolled Exotic Armor piece.