History of Breakneck (triumph)

How to complete

Complete the Breakneck mission, the fourth mission of the Destiny 2: Lightfall campaign, on Neomuna, on any difficulty. It needs the Lightfall expansion.

1. Clear the Vex from the Neptunian Reactor area. Stay back and destroy Cyclops turrets first.
2. Reach the reactor through the open facility full of Vex. Hold cover behind crates instead of pushing up, and destroy the Vex pillars.
3. Defeat Calixte, System Ward Finality (a three-phase Hydra). Shoot Detain Drones before they touch you.
4. Escape the building through the Strand vents past the Shadow Legion Cabal. The original two-minute timer was removed in a later update.
5. Defeat the two Tormentors. Freeze or suspend them to stun them and manage the Cabal adds.

Machine guns help with add clear, and crowd control is useful on harder difficulties.

Seal

The game text gives no seal or reward, and the pages I opened do not say which category lists it.