Vrai

The Vrai are an alien species originating from the planet Z'traa that invaded the Matoran Universe over 99,400 years ago and attempted to mutate its inhabitants into Vrai. Fortunately, the only island affected by the mutation virus was Stelt, which was destroyed by Blackout's army when he took over the universe.

Several Vrai were hidden in an unknown location and released by Jarr, and likely destroyed by Blackout's army, leaving no more Vrai in the Matoran Universe. A Vrai was sent to Bara Magna, and used a DNA scanner to create a complete record of Xeno's genetic structure.

The Vrai were finally forced to leave their own planet entirely when an experimental bioweapon was set off by Xeno, killing all lifeforms on it and sterilizing it for the next 10,000 years. Thanks to this, the Vrai experienced a shortage of resources, and proceeded to fight each other in a civil war. Apparently, Blackout decided to supply both factions with increasingly destructive weapons, planning to wipe them out.

This plan didn't work, and 50,000 years later, the Vrai were still around, once again inhabiting their original homeworld of Z'traa, which Blackout then blew up.

History
It is unknown when the Vrai came about, but it is estimated to be between twelve to sixteen million years ago. They quickly became the dominant species of their homeworld, made advances to their technology which allowed them to colonize their planet's moon, and were about to expand further out into their solar system when the population of Z'traa's moon decided they wanted independence, and a civil war began, which almost destroyed their civilization. The Vrai were only saved when an alien ship crash-landed on Z'traa, giving them access to technology centuries beyond their own.

Using their new technology, the Vrai rapidly took over a large area of space, and became one of the greatest powers in the known universe. Defeating a Vrai fleet was practically impossible, and dozens of races were enslaved by them. They would continue to expand, undefeated, until they encountered the Riders, resulting in an immediate military conflict. The Vrai had also encountered another major threat: the Great Beings (who had migrated from their destroyed homeworld of Spherus Magna to Mordor and other worlds). Despite the fact that the Great Beings aided them in the Rider-Vrai Wars, the Vrai the believed that they were a potential threat to them, and eventually attacked them. The war would go on for 100 years, and ended up spreading to the Matoran Universe, where it became known as the Vrai War. With the Toa and Makuta being unable to fight off this menace, the Great Beings created the Elite Makuta. They eventually succeeded in driving the Vrai out of the universe, but not before they unleashed a mutation virus on Stelt.

This was the end of the Vrai golden age, and their empire quickly shrunk to a mere fraction of what it once was. If that wasn't bad enough, a rogue Vrai called Xeno got his hands on an experimental bioweapon, and set it off, completely sterilizing Z'traa. A new civil war began, and Makuta Blackout planned to exploit this by supplying the factions with increasingly destructive weapons, leading them to wipe each other out. This didn't work, and the factions were finally united against Blackout in the First Battle of Impel Down.

Over time, Z'traa became habitable again, and the Vrai returned there. And then Blackout returned, and used the Twilight to devastate Z'traa once more.

A group of Vrai settled on a planet they baptised Neo Z'Traa, which later became a battlefield because of its protodermis reserves, and then was devastated by the Battle of Omega Supreme, which lead to the death of most of the colonists.

The remaining Vrai diaspora is scattered throughout the universe and whatever remains of Neo Z'traa.

Trivia

 * In French, 'Vrai' means "true". The significance of this is unknown.