Requirements: Must already have Quest and 540+ Light
Malfeasance Quest Steps:
Step 1: Visit the Drifter
Step 2: Defeat 25 Taken bosses/mini-bosses in the Dreaming City.
Step 3: Complete The Corrupted mission
Step 4: Deposit Motes. Dropped Motes subtract x2 score. Win Gambit matches. (seems to be 500 Motes and 10 wins)
Step 5: Have an ally invader defeat four opposing Guardians in a single invasion three times, OR defeat four opposing Guardians as an Invader. As an invader, defeat 25 opposing Guardians in Gambit.
If you do not have the Quest we can run gambit games for you here: Gambit Boosting (3 Matches)