Season of the Forge
From Destinypedia, the Destiny wiki
Season of the Forge (also known as Black Armory) is the fifth season of Destiny 2 and the first part of the Forsaken Annual Pass, starting on December 4th 2018 and ended March 5th, 2019. This season introduces the reclusive Ada-1 and the Black Armory as Guardians work to recover its Lost Forges and uncover the ancient history of the weapon foundry itself.
Season of the Forge is the first seasonal content in the Forsaken Annual Pass. It includes a new activity, raid, and many new weapons and armor to pursue. The story centers on a newly-formed Fallen terrorist organization, the Kell's Scourge, who have stolen from the Black Armory and are using its technology to terrorize Earth and establish a foothold of power in The Last City.
Black Armory was developed as part of the Destiny 2 Annual Pass, which are meant to be a smaller series of DLC releases that include new endgame activities, missions, and quests for Guardians to pursue. These include new Raids and activity types.