With your Challenger Medallion socketed, the Hammer of Proving is ready. Challenge a prospective Commander and pillage Caiatl's Tribute Chest at the end of a Battleground to disrupt their Rite of Proving. The Battlegrounds playlist may be found in the Director under Vanguard missions.
During your mission to foil Ixel, the Far-Reaching on Nessus, troubling data pulled from Vex prediction engines foretold a series of futures where Zavala has suffered a final death. Crow believes the Cabal will try to act on these predictions and that Zavala is in danger.