The M'Tar were a species claiming to be one of the oldest races in the known universe, with some claiming to exist in the universe before our current universe. As of 2367, they were native to a region of subspace known as the M'Tar Domain. (Star Trek: The Prospect Chronicles: "Lady Lazarus")
The M'Tar had evolved and shed their bodies, appearing as dark blue or black balls of energy with a blood red core. They have telepathic and telekinetic powers beyond any race encountered by the Federation to date. They are immortal due to a supposed "Fountain of Youth" they and their enemies, the Na'arbi, perfected.
Legend (purported history)
Captain Hahn Jun-Seok speculated that according to M'Tar and Na'arbi legend, the two races were created as different ends of the spectrum and would battle until the end of eternity, and that if that legend was true, the M'Tar could have existed in an universe prior to the Big Bang. The war between the M'Tar and Na'arbi was called The Great War.
Another legend also claimed that the reason for the Big Bang was an intergalactic war between the M'Tar and the Na'arbi, one which destroyed the majority of both sides' populations and both races' home galaxy. The legend stated that the surviving M'Tar created a weapon of such mass destruction, it caused instability in the expansion of the universe, and once fired, the weapon contracted their universe at an amazing rate. This contraction and then sudden expansion created the Big Bang, and the M'Tar, as well as the Na'arbi, survivors supposedly hid in a "pocket" of space not affected by the explosion.
In 2364, the M'Tar attacked the USS Artemis, killing 80% of its crew. For an unknown reason, the M'Tar activated a warp core breach, and the survivors evacuated the ship. While the Artemis appeared to explode, it in actuality jumped to warp. (Star Trek: The Prospect Chronicles: "False Security", "Lady Lazarus") At the time, Starfleet did not know it was the M'Tar behind the incident.
Upon arrival, the Prospect crew discovered the remnants of the Artemis. An away team, consisting of Commander Anne Lansing, Security Chief George Stratos, Counselor Daniel Radke, Garrett, Ralf Mendoza and Steven Tedesco beamed over to the wreckage (after environmental controls were brought back on-line) to search for bodies. They split up into three groups: Stratos and Mendoza on the bridge; Lansing and Tedesco in Main Engineering; and Radke and Garrett in the front section of primary hull (which was blown out into a wide, three-deck or higher area contained by a force-field).
Lansing and her escort discovered the warp core was not overloading at the time the survivors abandoned ship, but something or someone deliberately sounded the warning when no real threat existed. They bring the warp core back on-line.
All reported finding no bodies aboard the ship, even though so many of their colleagues had died that day.
The other teams converged on the area to find the Liaison and Link bound to the Artemis's frame by some sort of biological vine (tied into the Link's back, which, in turn, was wrapped around the Liaison's body). The M'Tar instructed the Prospect to prepare for them to board, proceed to Sector 001 and usher in the Eighth Great M'Tar Empire.
Unbeknownst to the M'Tar, their control on Radke weakened when they left his body to feed on corpses (the latest being Mendoza, whom Radke killed). Undercover Na'arbi agent Hahn Jun-Seok, revealing some of his true identity to Captain John Greene on the Prospect, transported over to the Artemis, exploiting this weakness. After setting the warp core to critical, Hahn enabled the Prospect to beam over Lansing and her away team, sans the transformed Radke and Garrett.
The Prospect pulled away as flashing emanated from the hull breach in the Artemis's primary hull. At the last moment, Hahn broke Radke and Garrett away from the M'Tar vine and transported them back to the Prospect before the Artemis exploded, sucking the debris, Hahn and the two M'Tar through the portal the M'Tar created into the M'Tar Domain. The portal collapsed with the explosion. Hahn sent a message to Greene to warn Starfleet Command the M'Tar were regrouping and repopulating. (Star Trek: The Prospect Chronicles: "Lady Lazarus")
Starfleet Command believed these M'Tar were two of a handful of M'Tar left alive after the Great War, and the M'Tar Domain could only open into our galaxy at regular (but greatly-distanced) intervals in time. The theory was the M'Tar originally wanted to use the Artemis to infiltrate the Federation while the conspiracy aliens attempted to take control of Starfleet. Unfortunately, they were left to drift for years (as their plan failed), but their new plan involved taking control of the Prospect and returning to enslave the Federation.
The Eighth M'Tar Empire
Had the Liaison and Link been successful in subduing the Prospect crew and Federation, they would have established the Eighth M'Tar Empire. This comment implies there were at least seven M'Tar empires which had risen and fallen by 2367.
In the Pendragon timeline, the M'Tar were believed to infiltrate the Milky Way Galaxy unhindered due to the Federation Civil War. They supposedly took control of the Myhr'an, growing their territory by three-fold. A Starfleet fleet, headed by Admiral John Greene, went to investigate, but instead confronted a Myhr'an fleet attempting to destroy the Federation planet Rhaandaran. (Star Trek: Pendragon: Other Knights anthology: "Gravity")
- It was never established but highly implied the M'Tar were behind the rise in Myhr'an power.
Attitude towards other races
The M'Tar encountered to date by Starfleet were extremely aggressive and hostile, believing they were the only beings in the universe with the right to exist as god-like while other races served their every need.
The M'Tar also did not speak a language that could be understood by any humanoid; thus their actions and intentions were often not understood, and their creation of a Liaison and a Link to communicate with other "lesser" beings came into play. The language barrier could be where the M'Tar's attitude towards other races originated from.
Later, it was discovered more than one Liaison and Link existed, and both the M'Tar and Na'arbi used these genetically engineered people as treaties, called Treaties. (Star Trek: The Cantabrian Expeditions: "White Flag")
Experimentation and mistreatment of other species
As a part of the Great War, the M'Tar indicated through their words and actions that the "lower" races were expendable in their mission to defeat the Na'arbi.
Destruction of non-compliant species
Anne Lansing, eminent Starfleet archeologist, discovered on one of her digs evidence that supported belief the M'Tar, millennia ago, would destroy the entire surface of a planet if its inhabitants did not comply.