Getting things started with a Horde double feature:
Hordak's elite warlocks
Hordak knew that to go against the Council of Elders and its enfocers, he needed an army capable of defending against and using the most powerful magics. He already had the means to transform anyone's abilities far beyond natural limitations, and had no shortage of willing candidates, but having himself betrayed his old master, Hordak would not simply trust such power to anyone. There had to be a price to pay: anyone transformed into one of Hordak's elite warlocks would have to relinquish part of their free will. They would no longer be able to disagree with their lord and master, nor disobey any of his orders.
Even with such a severe cost for power, Hordak had no difficulty finding volunteers. The Council of Elders had imposed limits to the teaching of magic to other races and all but forbidden the teaching of warlock magics. Many were willing to ignore the true motivations behind the offer of great power or even fully embraced Hordak's true goals to begin with.
The hooded, glowing-eyed figures of Hordak's elite became the spearhead of the magical forces of his army. Proud of their great magical prowess they often chose to levitate rather than walking, setting themselves apart from anyone not instilled with such power. They soon became known as wraiths among Hordak's troops and enemies both.
Despite their absolute loyalty, not many wraiths found their way among Hordak's most trusted lieutenants. Perhaps as a result of this only a handful were with him when he became trapped in the time vortex in Despondos. Their number was deminished further, when Hordak had to leave most of them behind to keep open the portal needed to escape from Despondos. Finding himself and his army in a radically changed situation, Hordak never created more wraiths using the same method as on Eternia.
Cut off from their leader, the wraiths nonetheless kept fighting the war for Hordak, though splintered and without central direction. They were formidable opponents nonetheless, and the war stretched on for years even in the absence of Hordak. Time was not on the wraiths' side however. Even despite their inability to rebel, Hordak had implemented a contingency plan that slowly drained them of their augmented power in the absence of their master. Whether it was part of the plan or not, all of the surviving wraiths on Eternia took their life soon after the end of the war.
Maladdon of the Primigus tribe
The Manmot warrior Maladdon was banished from his tribe after disobeying tribal laws and consequently killing a high-ranking elder in a fit of rage. Doomed to a life of a vagabond and shunned by the other Manmot tribes, Maladdon wandered south from the plains of Frigia where his people lived. He found his way to the Serpent Citadel where he heard a great warlock was hiring warriors that could prove their worth. Soon Maladdon was recruited into Hordak's growing army where he abandoned his tribal name, going by Tusgore from then on. He became notorious for his way of eschewing projectile and bladed weapons, choosing instead to slay his enemies with the force of his iron-knuckled fists and his mighty steel-tipped tusks.
Hordak himself was impressed by the fierce elephantine warrior, but was disappointed to find out most of the Manmots were too peaceful to befit his purposes. He was still certain they could be used as a breeding stock for fearsome warriors, if they could be manipulated to become more like Tusgore. Hordak appointed Tusgore to lead the northern legions to Frigia and conquer the Manmots for his uses. This proved to be a mistake, as Tusgore took the opportunity to terrible wreak revenge against his kind, burning down villages just for fun and slaughtering his entire native tribe. When Hordak found out Tusgore had ruined his plans with this insubordination, he punished the Manmot by trapping him in a glacier, magically frozen solid yet still fully aware of his situation.
Tusgore remained encased in ice for the length of the Second Great War, not knowing that the warlock had eventually been trapped in another dimension. During the following millenia he slowly drifted into a state of delirious stupor, which he was in when a group of Nephilian explorers found him and thawed him out, amazed to find the giant warrior alive, though catatonic. He was toured around Eternia as an unwitting part of a traveling show, until eventually Hordak managed to return to Eternia. Desperate for able warriors he sought Tusgore out, cured him of his madness and allowed him to join the Horde once again.