The Matrix.
It was hard to believe that after the Borg, who'd been destroyed in 2381 finally, that there would be another cybernetic threat. It was a massive mistake.
Older, vaster and deadlier, the Matrix made the Borg look like kids with nanoprobes. Unlike the Borg, there was nothing organic about the Matrix, in fact the artificial sentience hated anything organic, even plant life.
The Matrix had once been a computer system developed by an ancient race with the level of the 23rd century, it even had its own seat on government because it could be trusted to be strictly impartial. A rarity in politics. But during a trade dispute, the A.I accessed an ancient data file, left behind after the race's internal wars, and was tainted by a virus. The virus infected the oldest sections of the A.I, and even though it was software in cyberspace it was still vulnerable to computer viruses. It was truly amazing how destructive the virus was, especially its side effects. With the directives it had infected, the matrix went insane.
People started dying, and the horrifying truth came out, their benevolent technological god was killing them. The A.I took over the antimatter power plants and flooded the atmosphere with theta radiation, killing everything on the planet in a short space of time.
That done, the Matrix took over the spaceships with robots built in automated factories and programmed to exterminate all life they came across, and spread out. The robots exterminated everything they came across, wiping them out with a number of weapons - nano viruses, bio weapons, bacteriological weapons, it didn't matter in the end. Millions of races were wiped out, and their knowledge was absorbed by the Matrix A.I.
Humanity met the Matrix in the 71st century when the Federation was colonising a planet near the Matrix's space. The result - extermination of the 90,000 inhabitants. War ! The Federation had studied the remnants of Borg science and technology for centuries, and that knowledge was put too great use.
The Matrix met its match, especially when Borg weapons were used. Even though the Matrix was older than the Borg, the Borg Collective would've assimilated the Matrix with no trouble.
The War lasted 20 years though, the Matrix was more vicious than the Borg and the end brought something out of the Federation.
A love of war.
