Tirek

Lord Tirek is the main antagonist of the My Little Pony: Friendship is Magic season 4 finale "Twilight's Kingdom." He is a powerful demonic being with the ability to drain ponies' magic. He shares a lot of similarities with King Sombra and most Dark Spawn, argueability with Chernabog.

Role
Tirek and his brother Scorpan tried to take over Equestria, but when Scorpan became friends with Starswirl the Bearded, he came to appreciate Equestria and tried to turn Tirek away from his quest. Tirek refused, so Scorpan warned Princess Celestia and Princess Luna, who were able to imprison Tirek in Tartarus (possibly by using the Elements). When Cerberus left his post at the gates of Tartarus, however, Tirek was able to escape. Sometime after he began absorbing unicorns' magic. Celestia received a vision of this and sent Discord after Tirek. However, Tirek was able to manipulate Discord into betraying his friendship with Fluttershy and joining his side. Tirek began eating energy from pegasi and earth ponies to take away their flight and strength. Finally he went after Celestia, Luna, and Cadance, but finding their magic to be gone he imprisoned them in Tartarus. Discord thought Tirek didn't value him as a partner so Tirek gave him a necklace, saying that it was his only keepsake from someone close to him. Then Tirek saw a stained glass window of Princess Twilight Sparkle, and Discord explained to him who this new princess was. He and Discord captured Rainbow Dash, Fluttershy, Applejack, Pinkie Pie, Rarity, and Spike, and Tirek ate their power before doing the same to Discord, saying that his necklace actually came from Scorpan, and that Discord is as worthless to Tirek as Scorpan was. Growing to tremendous size from the magic he absorbed, Tirek attacked Twilight, and when he destroyed her library, she became enraged and fought him in an epic battle. The two were evenly matched, though Twilight seemed to have a slight advantage, so Tirek revealed the other Mane 5, Spike, and Discord, imprisoned in orbs. Tirek told Twilight to give him her magic and that of the three Princesses, and she agreed, so Tirek released all except Discord. Twilight told Tirek to release him as well. He accepted and then ate Twilight's magic, increasing his size to massive proportions. To thank her for her kindness, Discord gave Twilight Scorpan's necklace, which was the final key to the Tree of Harmony box. Unlocking it, the Mane 6 received Rainbow Power, which they used to blast Tirek with a rainbow not unlike the one produced by the Elements of Harmony, leaving him imprisoned in a cage in Tartarus with no power while restoring Equestria and the ponies to the way they were.

Powers / Abilities
Tirek has manifested the following abilities so far: *Magic Drain: In his first appearance Tirek is shown to be able to consume the magic of ponies, removing their cutie mark in the process - he seems to literally suck this magic into his mouth, like a more kid-friendly version of "soul stealing". A pony drained this way is completely stripped of all magic. Tirek adds the stolen magic to his own, increasing his size and power. The more magic he drains, the more powerful he becomes. After devouring enough unicorn magic, he becomes able to strip pegasi and earth ponies of their innate magic as well. At very high levels of power, he becomes able to strip even an alicorn or a draconequus of all magic. If Tirek drains the magic of every single pony in Equestria, he effectively becomes its God, able to single-handedly control all the aspects of the land that ponies normally regulate collectively.
 * Immense Strength: At high levels of power, Tirek displays an enormous degree of super strength. He is able to lift and throw boulders bigger than himself, and smash the ground to create a fearsome shockwave.
 * Demonic Magic: Tirek displays a degree of magical power consistent with the amout of magic he has consumed. At low levels of power, he is only able to fire a weak, paltry blast. After consuming enough magic he becomes almost unstoppable. He has displayed enormously powerful energy projection in the form of blasts and beams, the ability to create magical shields, high-level telekinesis, high-level magical entrapment, the ability to create portals, and more. His magic seems to be affiliated with fire. The way he casts spells is unique to him: instead of emitting magic directly from his horns, he instead forms a ball of infernal energy in the empty space between his two horns.

In the SAF series.
Tirek and Scorpan were actselly specally created Darkspawn by Chernibog and Architect meant to be a "Plan B" when the Draconquui first betrayed the darkspawn thanks to Tyranny, who he himself ended up betrayed by his own kind going soft on him. However, Scorpan turned out to be inferior creation, understood friendship, and betrayed his brother, while he got trapped in Tartarus. Cause of this, Chernibog desided to ignor Equestia ALLTOGATEHR until the Darkspawn were strong enough to tackle a surprisingly powerful planet. That day, never came thanks to the High Council. And when Tirek was defeated AGAIN, he was sure that since the Equestian Cerberus would never leave it's post again... That is, until a certain uuniverseal fox sticked his nose where it didn't belonged.