Call to Arms
From Destinypedia, the Destiny wiki
Call to Arms is a weekly challenge given by Lord Shaxx in Destiny 2.
Players must complete Crucible matches. Every completed match, win or lose, grants 2% towards the goal, and player kills grant a further 1% per every two kills, rounded up; a average match may net around 10%. Completing the Call to Arms rewards one Luminous Engram, which can drop Nightfall-quality loot.
The PvE equivalent of this activity is the weekly Flashpoint.