Sentinel battery

Sentinel batteries are items used to power Night Sentinel machinery. They are used to unlock bonus items in the Fortress of Doom.

Lore
Sentinel batteries are filled with the untainted essence bestowed upon them by the Elemental Wraiths before their imprisonment by the Hell priests for the purpose of creating Argent energy. While the Sentinel Energy is separate from Argent, it seems to be a mighty source of power on its own, being able to power the Fortress of Doom, along with other huge machines, and grant the Sentinels their enhanced strength. Ever since the Wraiths were imprisoned and slain, Sentinel Energy has been scarce, only found in the Sentinel batteries scattered throughout Hell, Mars, and Earth.

Sentinel battery locations

 * Exultia (1)
 * Cultist Base (3)
 * Doom Hunter Base (2)
 * Super Gore Nest (3)
 * ARC Complex (3)
 * Mars Core (3)
 * Taras Nabad (3)

In addition, extra batteries can be obtained by completing all challenges in a map.