Lord Tirek; The Centaurian Fiend.

King Sombra; The Tyrant of Fear.

Two of Equestria's most wicked enemies. Monsters driven by lust for power, hatred for all things, and pleasure in the suffering of others. Living symbols of evil to the inhabitants of Equestria. Sombra for his enslavement of the Crystal Ponies and waging war against the rest of Equestria. Tirek for attempting the drain Equesria of it's magic and destroy it.

What ponies do not know is that the two Princes of Darkness did meet each other.