Ransack the Hoard
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.
Lord Saladin means to debilitate the Cabal forces by eliminating their Commanders and seizing their supplies.