Datenaron is a nathrezim, freed from the addiction to the Burning Legion's magic like all demons recruited into the Illidari, the dreadlord has set out on his own personal journey to keep fighting against the Burning Legion after the final siege of the Black Temple.
The nathrezim was among the many demons at Outland when it was invaded and conquered by the forces of Illidan Stormrage. Observing the conflict from the darkness, the dreadlord deemed the planet's new rulers more worthy of his powers than his current "employees" at the Burning Legion, whose competence has, in his conception, declined drastically, which allowed "ridiculous defeats", mainly the War of the Ancients, Battle for Mount Hyjal and, finally, the defeat of Magtheridon.
Thus, Datenaron was among the immense hordes of demons recruited into the ranks of the Illidari, and like them, was freed of the addiction to the Burning Legion's magic, which the demon calls as his "greatest investment" to this day. The dreadlord served the Illidari with all his might from the day he joined up until its final defeat at Black Temple, using the best his abilities of trickery and deception had to offer whenever placed at the battlefield against the enemies of the Lord of Outland, except during the final siege of the Black Temple, in which he used said abilities to infiltrate himself into the ranks of the Alliance and Horde adventurers simply to escape from the place, as Illidan's increasing insanity and the immense sequence of defeats suffered by the Illidari had the dreadlord quickly change his mind about staying, as he thought that giving him freedom from the Legion's "petty magic" was their ultimate purpose, and they had outlived their use to him as soon as it was fulfilled.
No longer a member of the Burning Legion and with the Illidari dismantled, Datenaron's destiny was his to forge alone, and this perhaps is worse than having him bound to the cause of another above him. Datenaron has embarked on his own journey to rally a personal army with the intent of finding and conquering a realm for himself to use it as a staging point for his own assaults against the Burning Legion no matter the cost, so that he could continue from where the Illidari had stopped due to the insanity that progressively plagued its leadership.
In order to acquire such manpower, the demon traveled constantly between Azeroth and Outland under several disguises, saving the lives of many and tricking them into a pact that bound them to him, which granted him a considerable amount of mortal followers, many of which were trained in the warlock arts by himself with the purpose of enslaving as many demons as they could to both bolster the nathrezim's ranks and diminish the Legion's contingent since he didn't have the same means as the Illidari did to set such demons free from the Legion's magic. Another use for the mortals is sending them to the main cities of their home factions in incognito to serve as his eyes and ears, by way of his limited mental link with them granted by the curse they unwittingly accepted him to place on the day they joined his ranks, in order to track more potential additions to his cause.
Some demons also joined Datenaron willingly, many of which were survivors from Illidan's defunct forces. Datenaron also used the best of his demonic abilities to enslave lesser demons of his own, but also resorted to more sophisticated methods. Using the core of wayward voidwalkers to empower a summoning spell, the demon called forth three voidlords and promised them aid in dealing with their rivals in the Void with his and his followers' abilities in exchange of their servitude. Thus, the triumvirate of voidlords started spreading several of the true names of their most hated rivals to the nathrezim, which granted him power over all of them, forcing them out of hiding through torturous summoning rituals and enslaving them alongside his mortal apprentices. Thus, tamed demons of the Void became the corner stone of Datenaron's forces, in retribution, the three voidlords whom he first summoned were made into his closest lieutenants, known as the Triumvirate of the Void.
Aside from recruiting and pact-forging with mortals and subduing demons, Datenaron has also infiltrated himself in guilds of adventurers from both factions more than once, corrupting them from within and causing serious inner conflicts that resulted in the dismantling of said organizations, then using his fel magic to corrupt and bind the survivors of such turmoils, deemed the truly worthy additions by him, to his will.
This section concerns content exclusive to Mists of Pandaria.
The Alliance-Horde war was perhaps one of the best opportunities for the demon to bolster his ranks, the general lack of emotional and mental stability of several people caused by the stress and dread of the conflict allowed Datenaron to trick many into serving him. However, he would meet his first great obstacle at Ashenvale.
With his forces spread across the world to find fitting additions, Datenaron himself did so at Ashenvale, corrupting many battlers of both factions and using his dark abilities to subjugate their will while hiding behind the lines in the disguise of high ranking officials, even using the corpses of those whom nearly discovered his deception when necessary.
The demon went to Raynewood Retreat and saw a rich niche of new soldiers in the desperate dryads defending the settlement and the recklessly bloodthirsty orcs trying to overcome them and conqure the base. Thus, Datenaron secretly ambushed a party composed of a male night elf druid and two Sentinel escorts who were on their way to aid the dryads, the trio were no match for the dreadlord and were rapidly overwhelming, the druid's body being drained of its soul by the nathrezim's dark magic, who proceeded to possess the emptied carcass himself, using said spells to restrain the rotting. Datenaron thus rose the two Sentinels to serve as his guardians while in the region. From the inner building of Raynewood Retreat, Datenaron, protected by his two enslaved Sentinels, organized the creation of the Ashenvale "branch" of his army by tricking young and adventurous night elves into attacking the Burning Legion's settlements all over the region not only to raise their corpses with fel magic when they fell and enslave the weakened demons, but also to further divert attention from the main conflict between the oricsh invaders and the dryad defenders.
Datenaron's plans were eventually uncovered when his Sentinels captured a female orcish adventurer who, sent by the people at Splintertree Post to aid in defeating the dryads, was wreaking havoc on varying levels. Once the news reached Splintertree, Overseer Leugim led a Grey Legion strike force at Raynewood and, after a long battle that resulted in the destruction of his two corrupted Sentinels and eventually confronted the demon himself until he bursted the elf's carcass open and, after some time, retreated, but not before blasting the Grey Legion's members.
Later on, Datenaron ambushed Leugim and Soldier Li-Zai at the Howling Vale, in which he nearly overwhelmed the duo if not by the surprise arrival of Legionary Elite Tsukia Graceleaf, Soldiers Barttroz, Remulous and Criken. Datenaron turned Criken against the Legion by possessing her and rapidly bested Overseer Santangelo, but left her body after it became too damage and weak to channel his power through, thus escaping again, leaving the Grey Legion to fight against a corrupted Li-Zai, crazed by the residual power left by the dreadlord. Due to the sudden and heavy intervention of the Grey Legion in his plans, the demon enslaved the felguards and felhounds at Fire Scar Shrine and settled there, sending some of them to ambush Leugim and Soldier Kron'thar at the Howling Vale as the orcish warlock studied the site of the previous battle, using his abilities to track down the demon but be unable to provide proper coordinates due to the attack.
Days later, the Grey Legion, led by Overseers Leugim, Mol'Tsok, Mu and guided by Kron'thar, battled Datenaron's subdued demons all over Ashenvale before the path to Fire Scar Shrine was finally open. As soon as they arrived, Datenaron achieved the feat of rapidly summoning two Terrorguard under his will. While the forces of Mol'Tsok and Mu battled the two powerful minions, Leugim's group battled Datenaron himself. The demon proved too strong for them to defeat, the battle lasted for hours and all that they had succeeded was in weakening the nathrezim, after some more time, when Datenaron was weakened enough, Kron'thar casted an empowered banishment spell that bound the demon to Fire Scar Shrine, sealing his essence at it in order to prevent him from recovering at the Twisting Nether.
The dreadlord grew infuriated at the notion that a mortal had managed to seal him, and observed as the foolish Horde guild left Fire Scar, thinking themselves victorious. Kron'thar's seal won't last as long as any in the Grey Legion is expecting, it takes a lot more to seal such a demon. While not strong enough to break his seal yet, Datenaron resumed his forces' operations despite his current predicament by using his mental link with them.
His followers are working hard to strengthen the demon's forces and are preparing to shatter his shackles, so that their master can have his glorious return.