Scorpan

Scorpan is Tirek's brother, who is alluded to in the two-part fourth season finale episodes.

Development and design
Scorpan shares his name and design with a Generation 1 villain from the animated television special Rescue at Midnight Castle. He is a brown, gargoylish creature with a mane, bat-like wings, and a thin, tasselled tail. While he is depicted as Tirek's brother in the series, his G1 counterpart is a human prince who was cursed by, and reluctantly serves, Tirek, and he was a friend of Spike's G1 counterpart.

Depiction in the series
Scorpan is first mentioned in Twilight's Kingdom - Part 1 in a legend told by Princess Celestia and Princess Luna to Twilight Sparkle. In the legend, he and his brother Tirek come to Equestria from "a distant land" with the intent of stealing Equestrian magic. However, Scorpan comes to appreciate the ponies' ways, and befriends a young unicorn wizard. When Tirek remains resolute in their plan despite Scorpan's urges to reconsider, Scorpan alerts the Princesses of his brother's intentions, resulting in Tirek's imprisonment in Tartarus. Scorpan then returns to his homeland.

Tirek mentions Scorpan multiple times throughout the episode and Twilight's Kingdom - Part 2, contemptuous of his "weak-minded" brother's betrayal, and likening Discord's friendship with the ponies as "the same trap that claimed [Scorpan]". In a gesture of false gratitude and loyalty, Tirek gives Discord a medallion he claims to have received from "someone very close to [him]"; he later admits that it originally belonged to Scorpan, and actually considers the medallion "as worthless as he is."

Scorpan's gift later proves to be Twilight Sparkle's key for the Tree of Harmony's chest when Discord gives it to her in a more sincere gesture of friendship. This final key opens the chest and grants Twilight and her friends the power to defeat Tirek and seal him in Tartarus once again. Both the keys and the chest later leave the tree and go to Ponyville, where they create the foundation for Twilight's castle.