The arrivals season has started in Destiny 2, and features the new Umbral gear. This rather strange engram is covered with black residue. You can't open them on Cryptic, and instead rely on the Drifter to open them. You will need to play in the Facing the Dark quest.
Go visit the Drifter after you return to the tower with Eris Morn. The Drifter will ask you to take the Seed of Silver Wings, an item you obtained from Eris Morn in the previous mission, and complete the public contact event. You don't need to be successful in this field, you just need to complete it.
This public event is currently available on Io, as you can see in the image above. You just need to appear and Lost Oasis, then go there. Contact is a difficult public event and is played much like Gambit. You have to kill the enemies and collect the motes which they deposit, then deposit them in the bank.
Each full charge will spawn a wave of powerful enemies that you will need to defeat to advance to the next wave. This is a race against time, and if you get to the last part, you'll have to fight a boss to complete the event. If you complete it successfully, you'll get another Umbral Engram, and then you'll need to return to the Drifter to find out the next step.
When the evening is over, return to the Drifter and he will tell you to use his Umbral decoder. This is right next to it and will decode the Engram into an object for you.
That's it, there's more to the quest, but you can now open Shadow Engrams whenever you pick one up, all you have to do is bring it back to the Drifter and use the decoder.
