Juggernauts were ancient monsters set with the task of protecting the Void Pit.
Shortly after the elves awoke in Cuivienen, the Void Pit opened and the Ten Void Lords came out of it, bent on tormenting the people of Middle-Earth. They filled the pit with gold and other jewels. These jewels were corrupted with the powers of the void, so they became extra valuable. To guard their treasure hoard, Abaddon the Void King created the Juggernaughts with dark magic. These monsters slew anyone who found the Void Pit.
Juggernauts were huge, easily ten feet tall. They wore steel armor infused with the energy of the Void. They wore tattered crimson capes, and a helmet made of a troll's skull. They were soulless and empty under their armor, and it is told if one ever lost it's armor, it would become a black hole.
The Juggernauts were the perfect guards - silent, strong, determined. They could only obey orders from their creator, and they killed anyone who was not an ally of their creator.