Dark Aether

Dark Aether was created when a Leviathan from Phaaze crashed onto Aether, splitting it into two dimensions. Dark Aether is called as such because it is a twisted "dark" version of Aether and the "dark matter" in its atmosphere is damaging to "light" beings, such as humans, the Luminoth, and Space Pirates. Simply visiting Dark Aether can quickly kill creatures of the "light" universe unless precautions are taken. Dark Aether is home to the Ing, a race of shadow beings. Their connection to Phazon is uncommon as they are seemingly unaffected by its intense radiation. This is possibly because the Emperor Ing would have originally been a native creature that was corrupted to protect the Leviathan's core. It has also been suggested that as a result of the Leviathan creating the Dark Dimension, the Ing race may be the "mirror" counterpart of the Luminoth that inhabited the planet. However, this is very unlikely, as there are no dark "mirror" versions of other creatures that lived on Aether long before the Luminoth (Darklings, of course, do not count, as they are light creatures that have since been possessed by the Ing rather than entirely separate entites). Dark Aether is only accessible from Aether by Dark Portals. Since the two planets share the same space, they vie for planetary energy. Aether and Dark Aether were at war for about 70 years until bounty hunter Samus Aran fought on the side of the Luminoth. Samus successfully removed the remaining planetary energy from Dark Aether, destroying the Dark Dimension in the process. The Dark Dimension collapsed on Dark Samus but she survived.

The creation of Dark Aether split Aether's planetary energy into two halves, leaving both planets weak and unstable.

It is interesting to note that Phazon is only found within Dark Aether. Luminoth Lore seems to suggest that after initial impact on Aether the Phazon Meteor opened a rift to the Dark Dimension, landing in Dark Aether. This is supported as the Luminoth Lore data says that after the Luminoth emerged from their shelters the Phazon Meteor or any substantial crater was no where to be seen. Planetary scans of Dark Aether reveal a large crater and deep cracks running through half of the Dark Planet.

Sky Temple Grounds
Just like the light Aether counterpart, it's the surrounding area of the Sky Temple, though, it's a lot smaller that its light counterpart.This is where the emperor Ing itself makes its home guarding the greatest amount of planetary energy stolen from light aether.

Dark Agon
The dark version of Agon Wastes is mostly the same. The Ing are not very active on this area. The temple guardian of the area is Amorbis.

Dark Torvus
The dark version of Torvus Bog is a poisonous bog. All the waters of Dark Torvus Bog are poisonous making it twice as dangerous. It's also teeming with Ing activity after their defeat at Agon Wastes. The temple guardians of the area are the Chykka Larva and Chykka.

Ing Hive
The dark version of the Sanctuary Fortress is the hive of the Ing. In this area, the Ing are most active. The temple guardian of the area is Quadraxis.

Sky Temple
The final area of the game. The Sky temple requires 10 keys to access (Samus needs only 9, since one of the keys is already in place) and it is the home of the final boss of the game, the ruler of the Ing Horde: Emperor Ing.

Logbook Entry
Metroid Prime 2: Echoes "Can't determine origin of Aether's "dark twin." Contains high levels of Phazon ore. Native bioforms attack on sight."

Trivia

 * After Samus regains the planetary energy in Dark Torvus Bog, Dark Agon Wastes and Ing Hive, the sky in that area becomes red, unlike the normal purple. However, it cannot be seen in the Sky Temple Grounds or in the Sky Temple, even after the last planetary energy is recovered.
 * If Samus had retained her Phazon Suit from the first Prime game, she could have theoretically been able to withstand the atmosphere of Dark Aether, since its poisonous corrosion is a result of Phazon. This is also likely true of Phaaze.