Ihr was created nearly 2.5 million years ago by the Dark Lord as a part of it's defense project, which was intended to keep Xenon, the plague it created, safe from anyone seeking to avenge the places the Dark Lord had recently ravaged. The entire project was to create an alternate universe, which it did successfully, and then shatter any possible gateways between the "2nd universe" and the real one. However, one Toa of Wind managed to figure out the Dark Lord's plan and gave the command to create several "arks," or giant flying boats, that served as gateways between the 2 dimensions, and, as a coverup, the arks would also be transportation devices, designed to take supplies and passengers from one location to another. After a few Toa and Matoran showed up in the 2nd universe, the Dark Lord realized what had happened, and then proceeded to hunt down and kill the Toa of Wind. But the damage had already been done. The Dark Lord could not destroy the arks without heavily damaging it's precious universe on the other side. So the Dark Lord began a long campaign to hunt down these arks and either move them to locations where they could be guarded or simply crash them into planets and leave them there. Those that the Dark Lord captured, it moved to planets that had been overrun by Xenon. One of these planets was the planet Onex, and thus Ihr was born and assigned to guard the ark there.
Since Ihr was an original being of Xenon, he could not survive in the real universe, a flaw later realized and corrected by the Dark Lord. However, Ihr refused to let this stop him from serving the Dark Lord, and so he used Xenon infused Matoran and Toa to keep an eye on the planet and report to him if something happened. Nothing did for the first 2.49 million years, and Ihr slept peacefully.
The peace eventually stopped, however, when several Toa from the IUPD(a galactic government of sorts) found the location of Onex. Realizing that the infused Matoran and Toa would go crazy without a real, tangible leader that could exist in their universe, Ihr searched for and found a perfect stand in, a clone created of a reknown bounty hunter, MT(Toa Zehvor MT) called TM. Ihr offered TM a position in the ranks of the Dark Lord's army, and when TM declined, Ihr used a special type of Xenon to instantly enslave TM to his will. Thus TM became Ihr in Toa form, and wreaked havoc across the universe, destroying planets, enslaving entire species, and battling MT on multiple occasions(and winning with Ihr's immense power on nearly all of them). Eventually, the Toa Zehvor, a little known team of Toa, lead an attack on the planet of Onex and landed on the planet's surface. Three of them, MT, Tarakavarbiter, and Brenmac, found their way into the ruins of the ark, where they found a portal that took them to the 2nd universe.
There they found TM and Nightmare, a being that worked under TM and had been hunting MT and the others for the past half year. Ihr, deciding that 3 Toa were better than one, released TM from his control and revealed himself to Nightmare and the 3 Zehvor. Nightmare, angered that someone had dared enslave his leader, attempted to attack Ihr and was beaten senseless. TM quickly regained consciousness and tried the same thing, but had no success either. Ihr then made the same offer to the 3 Zehvor that he had made to TM 3 years ago, but was declined as well, upon which he knocked MT out and took Brenmac and TA prisoner.
Eventually, MT was awoken by 4 other Zehvor, Sonu, Mesonak, Mr. Matoro, and Burnmad. After MT explained what had happened, the 5 began to track down Ihr through the twisted paths of the alternate Onex. They eventually found Ihr, who proceeded to knock Mesonak off a cliff and then quickly rendered them unconscious again. Ihr was preparing the finishing blow when he was stopped short by three new combatants: Levacius(another Zehvor), TM, and Guilty Error, a Matoran who had been enslaved by Ihr as well. The latter two were quickly knocked away by Ihr, but Levacius managed to shatter both of Ihr's main weapons, leaving his power severly weakened. Ihr then called forth Brenmac's stolen "pet," a creature he had sent Nightmare to steal months ago. The "pet" was now enlarged to huge sizes, and, alongside Ihr, fought the Zehvor. The pet was defeated, but Ihr managed to knock the Zehvor down for a third time, and then announced his plans to sacrifice himself in order to destroy the Zehvor, claiming it was "the Dark Lord's will," with a countdown timer for the planet's self destruct being activated as he finished.
TM showed up on the scene and began fighting Ihr. Ihr playfully decided to mess around with TM, and the two eventually moved on to a bridge above a lake of floating Xenon. TM announced that, after what had been done with him against the Zehvor, that there was no way that Ihr would be allowed to kill the team. Ihr simply laughed, upon where TM tacked him to the ground and yelled at the Zehvor to cut the bridge, which Burnmad did. The bridge toppled over, sending TM and Ihr falling into the lake of Xenon, where they both were instantly overloaded with power and destroyed, but not before TM managed to blast a hole in the ceiling of the cave.
With Ihr's death came the collapse of that part of the 2nd dimension. The Zehvor were immediately teleported back to the real universe version, where TM's hole in the roof was still there. Mesonak, along with the newly freed Brenmac, TA, and Tahu, showed up, and escaped with the other 5 Zehvor.