Tirek

Tirek is the main antagonist of the Season Four finale episodes Twilight's Kingdom Parts 1 and 2. He is an escapee from Tartarus a dark land that serves as a prison for many horrific entities, and possesses the power to drain ponies of their magic. This Tirek is significantly different from his older counterpart - he has no army nor access to the Rainbow of Darkness, and instead relies on his own magical powers - but he shares the old Tirek's status as the most powerful and evil villain of his generation so far.

Development and Design
Tirek shares his name and certain aspects of his design with a Generation 1 villain from the animated television special Rescue at Midnight Castle. He is a centaur with dark reddish skin, white hair, black fur, cloven hooves, and is somewhat bovine in appearance.

Over the course of Tirek's appearances in the finale, his appearance gradually changes as he absorbs more magic. He intially appears very frail, with muted colors and a hunched posture that leaves him roughly at the height of a normal pony. After absorbing the magic of many unicorns, he gains a more muscular physique, brighter colors, and a pair of curved horns. His later transformations exaggerate his form even further, becoming larger, brawnier, and with increasingly long and elaborate horns.

In Rescue at Midnight Castle
He resides in the forbidden Midnight Castle alongside his minions and his servant/slave Scorpan, who he orders to kidnap the ponies of Dream Valley to execute his evil scheme.

Tirek wields the Rainbow of Darkness, a powerful satchel containing evil magic which corrupts everything it touches. It can even turn the ponies he captured into evil dragons which were used to pull his "Chariot of Darkness" and execute the event called the "Night that Never Ends", on which he will use the Rainbow of Darkness to corrupt Dream Valley and plunge it into chaos. When Tirek takes off in his Chariot of Darkness, Megan grabs the satchel containing the rainbow of darkness, but can't hold on to it. As he was about to release the Rainbow of Darkness, Megan opens the locket to reveal the Rainbow of Light. But it's only a small piece that is soon enveloped in darkness. But the Rainbow of Light starts fighting back, and eventually overpowers the Rainbow of Darkness. Tirek was destroyed by the Rainbow of Light, freeing Scorpan from his spell and turning him back into his human form.

In Twilight's Kingdom
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.

When Cerberus left his post at the gates of Tartarus (in episode "It's About Time; for unknown reasons) Tirek was able to escape. Sometime after he began absorbing a unicorn's 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 his medallion, 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 medallion 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 medallion 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.

Relation with Megatrain
Years ago, Megatrain had resurrected Tirek so he could steal energy but Tirek betrayed him and stole Megatrain's arc [which gave Tirek his ability to steal magic] then he put Megatrain in the prison of the Deceptitrains. Then when Tirek returned to Equestria, he discovered that Megatrain's machine was in one of the mountains of Equestria, but he was sent to Tartarus. Then when he returned again, he gained enough energy to be a god. But the Mane 6 defeated him and sent him back to Tartarus. Years later, Tirek returned seeking revenge and intending to start the machine up and use Megatrain's army of Deceptitrains for his own purpose, but found out that he needed the Matrix of Leadership in order to start it up. Optimus gave the Matrix to Thomas who had become a Prime himself, to prevent Tirek from succeeding along with the Blue Ruby and the Black Pearl. When Tirek had arrived in Canterlot looking for the Matrix he was denied to find out that it is only in posession of a Prime not the Princesses. When he come to Optimus and found out that he didn't have the Matrix, he froze him into an ice statue. Then found out Thomas had the Matrix, the Princesses raced to Thomas and warned him. But Tirek had followed and demanded Thomas to give him the Matrix. Blue Ruby, and Black Pearl. And if he did, he'd let him live to be his own train. But being loyal to Optimus, Thomas denied. In which Tirek blasted him, seemingly vaporizing him. But he inatvertinally activated a spell that brought Megatrain back. Megatrain was pleased to be free but then he took his fusion, plasma cannoin and vaporized Tirek completely for betraying him. When Tirek was killed pernamentally, Megatrain took back his Arc and got his energy back.

Origins
Tirek is one of Thomas, Twilight Sparkle, and Brian Griffin’s big and baddest villains ever. And he has a relation with Megatrain but he is also a disguiser. He is disguised as Mayor Adam West, the president of Quahog. After Spike told him that our heroes are engaging Diesel 10 and his squad. Then West reveals his true self, mentioning Megatrain and the dark side of the force, Spike surprises takes out his lightsaber and says “Your Tirek!”. Then Tirek says that Spike has great wisdom. After Spike saved Tirek, allowing him to kill Steeltoe he is his apprentice.

Powers
Tirek wields the Rainbow of Darkness, a powerful satchel containing evil magic which corrupts everything it touches. It can even turn the ponies he captured into evil dragons which were used to pull his "Chariot of Darkness" and execute the event called the "Night that Never Ends", on which he will use the Rainbow of Darkness to corrupt Dream Valley and plunge it into chaos.

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.

IDW comics
My Little Pony: FIENDship is Magic Issue #2 explores Tirek's "secret origins" at a young age, Tirek, a prince of his homeland, was instructed in the ways of magic by a centaur hermit named Sendak the Elder and became interested in pony magic through him. Tirek's ambitions greatly concerned his parents King Vorak and Queen Haydon.

When Tirek attempts to absorb the magic of a unicorn that Sendak captured, it backfires, resulting in an explosion that catches the whole kingdom's attention. King Vorak sends Sendak to the mines for his crimes, punishes Tirek, and returns the unicorn to Equestria. While confined to his castle quarters, Tirek plots to overthrow his father and rule over Equestria.

In Thomas' Adventures in Transformers Prime
In Thomas' Adventures in Transformers: Prime, Tirek's anti-spirit talks to Bowser in another dimension. Bowser was confused for a moment, then Tirek explains how he was cremated and that his anti-spirit has survived. And he now control's Bowsers body to travel to Cybertron, and he explains he want's to make his own Decepticons, and explains that he need another constitution for revenge against the Diesel Squad. When he is confronted by Thomas, Bowser deceives him, but Tirek groans him in pain. But when Unicron gets the Matrix he and Tirek get sucked in. When Megatron disbands the Decepticons, Bowser is still on Tirek's plan but is killed on the train chase.

In Return of the Big Bad
In Return of the Big Bad, Tirek's anti-spirt escapes and boy is he angered to the top. His spirit then created his body and is brought back and gather remaining Deceptitrains and makes them under his command. Soon enough they gather up enough power for Tirek to rull the world, but little did they know that Swellow is watching them. She flies back and explains Tirek has returned and is using remaining Deceptitrains for his command. Then the Mighty Morphin Power Rangers arrived and asked the same question. Then Tirek turns the kids from the Cul-de-sac evil, and they bow for his command. One the Deceptitrains shares about the Crystal of Train-Primes, in which now Tirek wants. He arrives to Canterlot, he injures the Diesel Squad and takes one of the castle peaks for his crown. And takes the foals as his prisoners. He then starts regenerating his army so they can take on the Island of Sodor. Meanwhile, our hereos ponder of how to defeat Tirek, and when Sheen brings up of how it's like when they defeated Bowser. In which Thomas decides it's time for Ultimus Primal to return. The Power Rangers used their Zords to combine Ultimus Primal in: "Super Ultimus Primal!". Tirek sit in his throne as the army is ready to strike, then Super Ultimus Primal walks up after destroying the whole army. Tirek however grows the same size as Super Ultimus Primal. But none the less, they get into a battle Tirek manages to uptang the upperhand for a moment, but then Super Ultimus Primal proves to be too powerful, but Tirek stands strong and doesn't give up, determined to lose this time. But Super Ultimus Primal, punches him square in the face then he fired his cannons at his chest and his eyes went on fire and kills. [simalar to how Obi-Wan kills Grievous in Revenge of the Sith] And his lifeless body falls to the ground, while Optimus sends a message.

Trivia

 * Tirek was originally a G1 villain who was the main antagonist of Rescue at Midnight Castle.
 * While Tirek was likely meant to outshine previous villains such as Chrysalis and Sombra, many fans hate him for destroying Twilight's library and sending the princesses to Tartarus. Some have even speculated, out of hate for Tirek, that after his reimprisonment, Cerberus eats him as punishment for sending the princesses to Tartarus. This is the exact opposite scenario of Chrysalis and Sombra; When they died, most fans denied it out of love for them or desire to see them return (and the IDW comics, whose writers are bronies and pegasisters, had Chrysalis survive, while some continue to deny Sombra's demise even after it was confirmed). This, in turn, could likely be the reason why Meghan did not have Tirek end up like his G1 counterpart.
 * In his fully-powered state, Tirek is easily the most powerful antagonist (and maybe even character) in G4 (much as he was in G1). After consuming enough magic, he surpasses even Discord in power (a character who is constantly portrayed as near-omnipotent). However, despite the raw power he possesses, he is not as skilled with it as the draconequus is. Tirek mostly uses the magic of others to fuel his own familiar offensive spells, rather than reshaping reality at will like Discord does.
 * He is considered as one of the most evil villain in Friendship Is Magic, along with Queen Chrysalis and King Sombra. However, while those two villains were never presented with any attempts at befriending them, Tirek is shown to have consciously flat-out rejected the very concept of friendship with the ponies of Equestria, his brother Scorpan, and Discord, believing it to be weakness.
 * His role in G1 and his relationship with Scorpan are given a nod in G4, but Scorpan is not shown outside of the flashback and the existence of Megan is not acknowledged.
 * He seems to be a sort of Satanic archetype for the show. He is obviously a demon, the most powerful antagonist of his generation, and beyond a doubt one of the most evil. He corrupts Discord into betraying the Mane Six, and his ultimate ambition is to rule as God of Equestria.
 * The fight with Tirek is also similar to Dragon Ball Z battles, and is considered the most epic moment of My Little Pony: Friendship is Magic so far.
 * Tirek bears a striking resemblance to Trigon from Teen Titans.
 * Tirek is the second main antagonist that is the main villain of a season conclusion (the first being Queen Chrysalis).
 * In his first appearance, Tirek bears a striking resemblance to Darth Sidious, Ring Wraiths, and Dementors.
 * Tirek is the second main villain to be directly involved with Discord in an evil plan, the first being the Plunderseeds which were created by Discord.
 * The sound effect that is heard when Tirek absorbs pony magic is the Xenomorph Queen's screech.
 * Lord Tirek appears to be the oldest villain in the My Little Pony franchise, as he was in his age when Star Swirl the Bearded was a young unicorn. The second ones are the Dazzlings, who were in their age when they were defeated by Star Swirl.
 * Lord Tirek is similar to Cell from Dragon Ball Z as:
 * They both gain power by absorbing it from the native inhabitants:
 * Tirek absorbs magic from ponies and powers from the mixels.
 * Cell absorbs bio energy from humans.
 * They seek out a specific source in order to become all-powerful:
 * Tirek wants to steal the magic from the Alicorn Princesses to become God-like.
 * Cell has to absorb Androids 17 and 18 to reach his perfect form.
 * Both have convinced a former villain to turn on their new allies to aid them:
 * Tirek convinced Discord to help him in exchange for freedom.
 * Cell convinced Vegeta to help him absorb 18 so that he can provide more worthy challenge.
 * Both have fought the main protagonist to a standstill:
 * Tirek fought Twilight Sparkle while she possessed all the alicorn magic until he bargained to let her friends go in exchange for it.
 * Cell fought Goku in an equal match until the latter quit to allow Gohan to fight in his stead.
 * Both were eventually defeated by the main protagonist, who gained power even greater than their own, along with their allies and the villain that they convinced to help them.
 * Tirek was defeated by Twilight and her friends when they gained great power from the Tree of Harmony after receiving the final key from Discord, who had ultimately learned true value of friendship.
 * Cell was defeated by Gohan as a Super Saiyan 2 while the Z fighters attempted to take him from all sides, but ultimately it was Vegeta who gave Gohan the opportunity to focus his true power and destroy him.
 * Tirek is also Aku's partner.
 * Tirek will become Thomas' enemy in Thomas' Adventures of My Little Pony Friendship is Magic - Twilight's Kingdom (Full Movie)
 * Tirek will get his revenge on Thomas and Twilight in Thomas, Twilight Sparkle and the Adventures of Rocky and Bullwinkle, Thomas and Twilight Sparkle Visits The Haunted Mansion, Thomas and Twilight Sparkle's World of Color, Thomas and Twilight Sparkle's Adventures of Disneyland Fun, Thomas and Twilight Sparkle's Adventures of Disney's Villains' Revenge and Thomas and Twilight Sparkle in Fantasmic (Walt Disney World Version).
 * Tirek will become Brian's enemy in Brian Griffin's Adventures of My Little Pony: Friendship is Magic - Twilight's Kingdom and will guest star in Brian Griffin's Adventures of The Lord of the Rings: The Return of the King and sends the Princesses to Tartarus, Brian Griffin's Adventures of Star Trek, Brian Griffin's Adventures of Transformers: Age of Extinction and Brian Griffin vs. The Mummy: Tomb of the Dragon Emperor.
 * Tirek became Aku's General in The Night to Remember.
 * Tirek is killed in Brian Griffin vs. The Mummy: Tomb of the Dragon Emperor but returns in Brian Griffin's Adventures Chronicles.
 * He will appear in Team Robot in Pokémon the Movie: Hoopa and the Clash of Ages.