Stygian

Stygian, also known as the Pony of Shadows, is a male unicorn and the antagonist of the season seven finale Shadow Play. He is a battle strategist and friend of the Pillars of Old Equestria who turned into an evil pony of darkness. His alter ego is first mentioned in Castle Mane-ia and depicted in.

Development and design
Stygian has a similar body type to Snails, Bags Valet, Gizmo, "Frazzle Rock", "Burdock Hooffield", "Street Rat", "Spiral Notepad", S06E24 Unnamed Pegasus Mare #2, S07E02 Unnamed Earth Stallion #1, and S07E19 Unnamed Earth Mare #2 and somewhat resembles S06E23 Unnamed Unicorn Stallion #2.

The word "stygian" means "dark and gloomy" and also relates to the river and deity Styx of Greek mythology.

Depiction in the series
The Pony of Shadows is first mentioned in a ghost story told by Applejack in the season four episode Castle Mane-ia. According to Applejack, when Nightmare Moon was banished to the moon, traces of her dark magic stayed behind. When night falls on the Castle of the Two Sisters, that dark magic takes the form of the Pony of Shadows.

In the season seven finale Shadow Play - Part 1, the Pony of Shadows is revealed to be a real figure from Equestrian history. As recorded in the lost journal of Star Swirl the Bearded, the Pony of Shadows was originally a normal pony who brought the Pillars of Old Equestria together to save the land from a great evil. However, the pony soon became jealous of the Pillars' power and glory, and he stole artifacts from them in a quest for power, resulting in his exile. The resentful pony thus turned to darkness for revenge and transformed into the Pony of Shadows. In order to stop him, the Pillars sealed him in limbo along with themselves. A thousand years later, Twilight Sparkle and her friends inadvertently release the Pony of Shadows from limbo when they free the Pillars.

In Part 2, the Pony of Shadows—weak from his time in captivity—escapes to regain his strength from the darkest corners of Equestria. The Pillars eventually reveal the beast's true identity as their former friend Stygian, a young scholar who gathered them all together to defend the realm and worked alongside them as a battle strategist until he stole their artifacts and transformed into a wicked creature of darkness.

The Mane Six and Pillars eventually track down the Pony of Shadows to the Hollow Shades. Before the ponies can banish him to limbo again, Twilight and Starlight Glimmer reach out to the real Stygian inside the beast's body. Stygian reveals that he never wanted to steal from the Pillars; he wanted to make copies of their artifacts so he could fight alongside them in battle. The Pillars realize their grave mistake, and together with the Mane Six, they free Stygian from the darkness and banish the darkness to limbo with the Elements of Harmony. Star Swirl apologizes to Stygian for letting pride cloud his judgment, and Stygian remains in the present era with the Pillars.

IDW comics
Stygian is first alluded to in the Issues #51-53 story arc From the Shadows by his descendant Shadow Lock, who seeks to erase all evidence of his ancestor's existence in order to prevent his return. Stygian is also depicted as the Pony of Shadows in Star Swirl's journal on page 20.

Stygian also appears on cover B with the Pillars of Old Equestria. In the story's flashback, his village comes under the Dazzlings' hypnotic control, and he leaves to gather together a group of legendary heroes strong enough to fight them. In, Stygian successfully recruits Rockhoof after helping him protect his village from ferocious lumber bears, and the two seek out Mage Meadowbrook together.

Chapter books
In chapter 11 of Discord and the Ponyville Players Dramarama, Torch Song of the Pony Tones mentions the Pony of Shadows.

Merchandise
In the Canterlot Nights expansion set of Enterplay's collectible card game, card #161 U is of the Pony of Shadows, which gives the description "A figment of the imagination, or an ancient evil bent on revenge? Either way, scary!"

Quotes
"You summon me at your peril, Star Swirl! Once I defeat all of you, this realm will embrace the darkness as I did so long ago!"

- Shadow Play - Part 1

"Drawing me here will only make me stronger. You will never defeat me!"

- Shadow Play - Part 1

"Don't fret. When I extinguish the light and hope of this miserable world, you won't remember any of this."

- To Twilight Sparkle, Shadow Play - Part 2

"Your days of glory are through, Star Swirl. Now my dark power will reign, and you six will bow to me!"

- Shadow Play - Part 2

"When you turned your backs on me, I discovered this place. The darkness spoke to me of a power beyond any I could imagine, and I listened. The shadow and I became one. Soon, all of the realm will be the same. Then all ponies will feel the despair I did when you cast me out!"

- Shadow Play - Part 2

"The darkness welcomed me when no pony would, and I will do what I must to protect it!"

- Shadow Play - Part 2

"I... I want to believe you... [growls] But the darkness will not be stopped!"

- Shadow Play - Part 2