The Overlord

The Overlord is an evil spirit who serves as the main antagonist of seasons 2 and 3 of LEGO Ninjago: Masters of Spinjitzu and the main antagonist of My Little Pony Transformers Prime: Twilight's Kingdom.

History
When the First Spinjitzu Master created Ninjago, the Overlord was brought to life and battled the First Spinjitzu Master for Ninjago. But before the Overlord could claim Ninjago, the First Spinjitzu Master split Ninjago in half, with the Overlord banished on the dark half.

My Little Pony Transformers Prime: Twilight's Kingdom
The Overlord later returned to Equestria, intent on stealing all Equestrian magic and having it for himself. But Lloyd Garmadon defeated him and the Overlord was sent to Tartarus, but later

My Little Pony Transformers Prime: The Cutie Re-Mark
When Twilight, Optimus, Spike, and Starlight

Appearance
In his first form in My Little Pony Transformers Prime: Twilight's Kingdom, he

Ninjago: Masters of Spinjitzu

 * The Stone Army
 * The Day Ninjago Stood Still
 * The Last Voyage
 * Island of Darkness
 * The Last Hope
 * Return of the Overlord
 * Rise of the Spinjitzu Master
 * The Surge
 * The Art of the Silent Fist
 * Blackout
 * The Curse of the Golden Master
 * Enter the Digiverse
 * Codename: Arcturus
 * The Void
 * The Titanium Ninja

Trivia

 * It is unknown if his spirit can be destroyed. As Zane said "Defeated yes, but can he be destroyed?", it might imply that the Overlord's spirit is indestructible.