This is a Roleplay Setting piece, much the same as Olga's Dwarf Anatomy, done by SquishyInk.

This is a creature called a Dark Rider.

It's the Honor Guard for the Dark King of a necromancer city known as Nef'Rel, found in the high peaks of a frozen winter wasteland. Formerly a living Drow Merchant, after an abortive attempt to cheat the royal family on a deal the Merchants were all executed and brought back as Revenants to serve the crown.

The women were brought back as seductive assassins known as Dark Archers, while the men were brought back as little more than a tortured soul, bound to their rune-engraved skull and placed in a hooded suit of ebony armor. Each Dark Rider is unique, and almost entirely immune to damage or destruction. As long as their skull remains intact, they can be brought back, and the runes act as wards to protect the skull from harm.

The Dark Riders rarely leave the palace, a citadel known as the Black Spire that towers over a monstrous black marble square at the heart of the city. The plaza is actively patrolled by Archers, Riders and hulking creatures known as Wardens, with the Riders usually mounted on their skeletal war steeds (also clad in black armor).