Lost Forges is an activity type introduced in the Black Armory downloadable content pack for Destiny 2: Forsaken. This activity is a 3-player Horde activity similar to Escalation Protocol and supports matchmaking.
This activity consists of three waves of enemies, two of which have special blue enemies that drop batteries for the forge.
In the 2nd wave of all forge activities, two drones (similar to the saboteur drones) spawn in different locations. Taking them out provides the players with the perk "Maximum Temper" that provide an extra rewards chest at the end, and is also vital to the mystery box quest.