History of Nightmare Containment Completions

Overview

Nightmare Containment Completions is a Triumph in Destiny 2 that tracks successful completions of tiers in the Nightmare Containment public event. The event takes place in the Castellum, the landing zone of the Derelict Leviathan on the Moon, during Season of the Haunted.

How to complete

1. Open the Director, go to the Destinations map and choose Nightmare Containment. Load in with the "Containment" option, which matchmakes you with players there for the activity.
2. Walk to the red Season of the Haunted marker next to the public event banner and interact with it to plant your Nightmare Harvester. Starting it costs nothing.
3. Tier I: clear the Scorn and Cabal waves, collect Shards of Dread, and deposit the Cores of Dread that Dread Bearers drop at the Harvester. Calus then interrupts, and you must kill two Egregore Atavists. The boss is Valus Thu'ur, a Colossus.
4. Tier II follows the same pattern with four Atavists. The boss is Primus Or'sek, a Centurion.
5. Tier III is a boss fight against Nightmare of Elykris, Nightmare of Anaphex or Nightmare of Navôta. Damage it to two-thirds health. It then shields itself, and you must destroy six Resonant Splinters while two Emissaries are killed. Repeat at one-third health.
6. After Tier III, wait about two minutes before starting Tier I again.

Defeating each of the three Tier III bosses at least once is the Tritainment triumph. Reported Tier III boss rotation varies between daily and weekly across guides.