Early in the war, the Luminoth learned that the Ing utilized energies comprised of pure darkness, and were primarily made up of the same energies. They believed they could kill the Ing by overloading them with dark energy. To that extent, the Luminoth produced the Dark Beam, which would utilize dark energy. After testing the weapon, it was learnt that the Ing are able to ignore the shots of the Dark Beam, having been born in a world ravaged by harsh dark forces. The Dark Beam was decommissioned and repurposed for opening portals to Dark Aether, and later for operating Light Crystal Mechanisms.
The Dark Beam is well suited for use against enemies found on Aether, as for obvious reasons it is useless against the Ing. Like other Luminoth beams, it uses ammo to fire. The beam's ammo can be replenished by getting an ammo pack dropped by an enemy killed by the Light Beam. If ammo has been depleted, the beam can be charged up to fire a weaker shot, which should only be used for interacting with Light Crystal Mechanisms (if you have to).
When used with the Charge Beam, the Dark Beam fires the Entangler, a blast of Dark Energy that freezes an enemy with Dark Energy tendrils. An add-on for the beam allows it to fire a devastating blast of Dark Energy that tears open a temporary Black Hole. The rift damages all nearby enemies and sucks in small enemies and flying enemies. If used on a Light Crystal, it cancels out the Crystal's energy and deactivates it. While this may seem like a setback, deactivating a Light Crystal will reveal any Lumites, who are able to perch the Safe Zone to become invisible and use the light to fire a "Solar Beam" at Samus. Without the Crystal, they are unable to hide and will be left with their weak vomit attack. A Crystal can be reactivated by shooting it with the Light Beam, Power Beam or Annihilator Beam.
- Metroid Prime 2: Echoes (First appearance)