The Pocket universe species are a mysterious, technologically advanced race of aliens originating from a Pocket Universe separated from our own. They are capable of tesseracting through solid matter, turning invisible and become intangible, phasing in and out of space.
The species are on average about 1.8 meters tall, and are extremely acrobatic and flexible, and have extremely good hand to hand combat skills. They also have superior strength, as is shown when they are fighting Rommie and are about equal in strength to her avatar. However, this strength might be the result of an exo-skeleton integrated with their armor. They also know some kind of martial arts, as shown by their fighting skills.
The aliens sent tens of thousands of warships through their dimensional portal. With Trance Gemini's knowledge of the future in the current timeline, the Andromeda Ascendant and a Sabra-Jaguar Pride fleet were able to fight and defeat the aliens. However, even with knowledge of how to fight the aliens, Sabra-Jaguar sustained heavy losses, and the Andromeda was damaged. However, the aliens' invasion of Known Space was halted when the Eureka Maru launched a modified Nova bomb into the horizon of the portal, preventing the aliens from their objective. ("Tunnel At The End Of The Light", "If The Wheel Is Fixed")
A year later, a new group of aliens stole parts and equipment from ships within the Known Worlds in order to construct a generator to make a portal. This generator appeared to be less efficient than the one used in their home universe during the previous invasion and the aliens were unable to regulate the power levels required in order to establish a new portal, whether this was because of the inferior components used in its construction or the limited resources available to them in the Known Worlds was never established.
In an attempt to rectify the problem a group of the aliens assaulted the Andromeda Asdcendant and kidnapped Rommie's avatar, using an energy bladed knife to 'stun' her long emough for them to use a short-ranged portal to transport her off the ship. Once back at the location of the generator, Rommie was wired into the central control system so that her own systems could help to regulate the power flow long enough for a universal portal to be opened.
Tracing a homing signal Harper had built into the avatar, Dylan and Tyr were able to locate the generator and landed on the planetoid in slipfighters. With Rommie assisting them by disrupting the aliens' invisibility the pair were able to make their way to the generator control centre and free the avatar. Rommis then used equipment carried by her rescuers, including two force lances, some grenades and at least one datapad, to construct a timed demolition charge to destroy the generator before returning to the Andromeda Ascendant.
The explosive device successfully detonated just as millions of alien ships were about to emerge from their portal. Without power for their engines, the invading ships were pulled back into the portal.
Immediately after the Andromeda defeated the aliens, an lone alien appeared up on the bridge and strangely did not show any aggression. It offered Captain Dylan Hunt a knife, hilt first. After Captain Hunt accepted the knife, the lone alien collapsed and disappeared. ("Delenda Est")
In an alternate future, where the Commonwealth Charter was about be ratified by its member worlds, the aliens began hunting down the delegates one by one, leading the delegates to return to their own worlds separately.
Without a unified fleet to stem the tide of invading forces Captain Hunt and the Andromeda were forced to use a Nova bomb delivered into a local star by the Eureka Maru in order to try and destroy the invisible fleet in a single attack. Due to some undefined error on Trance's part only she and Beka Valentine, who had been crewing the Eureka Maru at the time, survived the attack.
This is one of the events that caused the older Trance Gemini to go back in time and switch places with her younger self.
The technology of the aliens is extremely advanced, as is demonstrated by their ability to create wormholes at will in order to travel between dimensions. Not only can they make an extremely large wormhole, but they can also create small localized ones and position them with accuracy. As Rommie notes, it would take the power of every sun in the Andromeda galaxy in order to create such wormholes. This means that they have become a Type III civilization on the Kardashev scale, which means that they use approximately 4.0×1036 yottawatts. They also apparently have the ability to tesseract over short distances, can become invisible, and they and their ships can phase through solid matter and space.
The aliens use full reactive body armor that they wear at all times. It has 5 to 7 retractable, serrated blades built in. The armor also provides protection for the legs and torso. The helmet component has a built in HUD (Heads Up Display), infrared and ultraviolet scanning, and a built in target identifier and designator. Judging from the strength of the armor's users during combat, they may have a built-in exo-skeleton.