Lord Tirek

Lord Tirek is the main antagonist of the season four finale episodes. He is a villain who escapes Tartarus and steals magic from ponies.

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 reddish skin, a white beard, and black fur, and is somewhat bovine in appearance. As the episodes progress, his appearance gradually changes from a frail, pony-sized stature to a tall and robust one, with increasingly pronounced and curved horns.

During her May 2014 takeover of the Hub Network's Twitter feed, Meghan McCarthy identified Tirek as her "new favorite character", and described Tirek as having "some serious issues and some serious magic". On May 10, 2014, Jayson Thiessen tweeted "hehe" in reply to a fan's tweet "Was just rewatching episodes with a friend. Was that Tirek at the end of Castle Mane-ia? My mind may have just blown."

Depiction in the series
Tirek appears in Twilight's Kingdom - Part 1 in a frail, weakened state. In a Canterlot alleyway,  he approaches the unsuspecting unicorn Rare Find and drains his magic, growing larger and more powerful. This attack is sensed by Princess Celestia and Princess Luna in a vision, who convene with Princess Cadance and Princess Twilight Sparkle over Tirek's origins.

In a narrated scene similar to the opening scene of the first episode, it is stated that Tirek came to Equestria from "a distant land" long ago, along with his brother, Scorpan, intent on stealing the land's magic. However, Scorpan grew to appreciate the ways of Equestria and even befriended a young unicorn wizard. Scorpan pleaded with his brother to abandon their plans, but Tirek refused to relent. To save Equestria, Scorpan informed the Princesses of Tirek's intentions, leading to Tirek being imprisoned in Tartarus for his crimes while Scorpan returned to their own land.

Celestia states that Tirek likely escaped during the events shown in It's About Time, when Cerberus left his post at Tartarus' gates, and is only acting now after recuperating from languishing in Tartarus for centuries.

While recovering his lost strength by devouring unicorn magic, Tirek is captured by Discord, who is acting on behalf of his friendship to the ponies. Likening Discord's actions to those of his "weak-minded brother", Tirek appeals to Discord's former nature as a master of chaos, convincing him that friendship is "a new form of imprisonment", and that betraying the ponies will grant him freedom to do what he pleases. With Discord's aid, Tirek absorbs enough unicorn magic to be able steal the magic of Pegasi and Earth ponies as well.

In Twilight's Kingdom - Part 2, Tirek turns his sights to Alicorn magic. Anticipating this, Celestia, Luna, and Cadance transfer all of their magic into Twilight and send her into hiding, believing Tirek knows of only three princesses. Arriving in Canterlot, and discovering the three to be of no use to him, Tirek banishes them to Tartarus before giving Discord a medallion originally belonging to "someone very close" to him, as a token of gratitude and loyalty. He then sees a stained glass depicting Princess Twilight, and learns from Discord that a fourth princess lives in Ponyville.

After the two arrive and capture Twilight's friends, Tirek absorbs their magic and grows even more powerful. Discord is thrilled by the prospect of ruling Equestria alongside Tirek, but Tirek says Discord is no longer of use to him and absorbs his magic as well; when reminded of the medallion he gave Discord, Tirek says the medallion was given to him by his brother Scorpan, considers it to be "as worthless as he is".

Tirek finds Twilight, who battles him in an explosive and destructive duel using the magic bestowed on her by the princesses. Noting their powers are evenly matched, Tirek offers with Twilight a trade: the release of her friends in exchange for the Alicorn magic. Despite her friends' protests, Twilight agrees to trade the magic for her friends, including Discord. After releasing them, Tirek promptly absorbs all of Twilight's magic, making him all-powerful.

However, Twilight and her friends discover Tirek's medallion is the final key to open the Tree of Harmony chest, and do so before Tirek discovers and attempts to stop them. The chest bestows the ponies with a new, powerful magic that Tirek is unable to overpower. With this magic, the ponies reduce Tirek to his weakened state once more. He is last seen locked in a cage within Tartarus, guarded by Cerberus.

Personality
Tirek displays narcissistic tendencies, his most obvious one being his obsessive desire for power. He can also be very manipulative and has a talent of making great sense and making persuasive points when trying to strike a deal.

However, he has little regard for following his end of a bargain, and is bitter and traitorous, not hesitating to turn on and dispose of anyone whose usefullness has expired, for example Discord.

He harbors a deep resentment for his brother Scorpan, describing him as "weak-minded" and "worthless".

Powers and abilities
Tirek is one of the most potentially powerful magic users in the show, as evidenced by his magical battle with an empowered Twilight Sparkle. Once freed from Tartarus, however, his magic is severely drained, forcing him to leech off of unicorns' magic and grow stronger. With Discord's help in rounding up the other pony types, he is able to absorb the power of Earth ponies and Pegasi as well.

Once he absorbs the magic of the Twilight's friends and Discord, Tirek gains enough power to be able to stand up against Twilight Sparkle, who at the time is empowered by both her own innate Alicorn magic and that of her fellow princesses. His subsequent deal with Twilight shows that he can also control Discord's powers of chaos, demonstrated when he snaps his fingers and brings Twilight's drained friends and Discord to her in soap bubbles. After he absorbs Twilight's Alicorn magic as well, Tirek grows from his already-impressive magnitude to a size comparable to that of a hydra.

Tirek's magical prowess after absorbing the magic of nearly every pony in Equestria puts him on equal standing with a magically empowered Twilight. He shrugs off a blast of Alicorn magic by simply crossing his arms and creating an energy shield; then he telekinetically slams her into a mountain and rams her through said mountain with his horns. Tirek's own magic beams manifest from a glowing orange orb that forms between his horns, sparkling with black electricity.

Quotes
"'Is he friend, or is he foe?' the pony wonders. I can assure you... I am no friend. I am Lord Tirek, and I will take what should have been mine long ago."

- Twilight's Kingdom - Part 1

"How does it feel knowing that every Pegasus, unicorn, and Earth pony will bow to my will and that there is nothing you can do to stop it!"

- Twilight's Kingdom - Part 2

"Give my regards to Cerberus!"

- Twilight's Kingdom - Part 2