Defeat Champions or defeat Guardians in Gambit and Crucible matches.
Crow believes that the Traveler is trying to send a message through the visions he is experiencing and is asking you to show him what it means to fight like a Guardian.
"I think Crow might be right. About this being a message, I mean. But I think it's more than just Hawkmoon; I think everything we've done and everything we've learned is all part of the same lesson, I just… I feel like we're missing a piece." —Ghost