Nox Suzaku

The Darkness of Suzaku is an entity and optional superboss in Final Fantasy Type-0. It first appears in the game's introductory sequence, there called "???." In subsequent playthroughs it can be found throughout the storyline and fought at the player's discretion.

Appearing
The Darkness of Suzaku's appearance is based on the player's collection of Phantoma, and is somewhat random - it is possible to defeat it and it will immediately appear again. Once it appears, the player is given a notice of such. Until the Darkness of Suzaku is defeated, all Phantoma the player collects will instead be absorbed by the creature. It may go away once it absorbs enough Phantoma.

Once the Darkness of Suzaku has appears, the player can find it in the air on the world map and approach it in the airship to battle it.

Battle
The Darkness of Suzaku transports the party into a dark void, where shades of other characters and monsters in the game, including Class Zero themselves, will attack the player in waves. Defeating all of them will dismiss the Darkness of Suzaku but not defeat it. The Darkness of Suzaku itself only appears in the battle when a member of the player's party is defeated, when a head of the creature will emerge from a portal to gather that fallen party member's Phantoma. At this time the player can attack it, and if a Kill Sight hit is landed, the creature will be stunned for a time and be vulnerable for longer. The Darkness of Suzaku is Level 200 and the shades it spawns Level 99, so the player is advised to be close to or at Level 99 themselves to fight it.

When the Darkness of Suzaku is defeated, the player receives a reward in-line with tandem mission rewards, based on their time to win, the collected Phantoma, and the party deaths. An S-Rank will reward them with a Crystal Fragment and a Megalixir.

Note that the Darkness of Suzaku can reappear even once defeated.

Nature
It is never clearly explained what the Darkness of Suzaku is, only that it is attracted to Class Zero and absorbs Phantoma. One theory is that it is an amalgamation of all expended Phantoma Class Zero has used, or possibly the Phantoma of Class Zero themselves from a previous cycle of Orience's history. The latter theory is supported by the fact the Darkness of Suzaku only appears after the first playthrough, and would explain why spectres of Class Zero themselves are among the enemies it spawns. The Darkness of Suzaku also looks like an avian entity, tying into Suzaku's guardian beast, the Vermillion Bird.