It is adorned in thick metal armor, and carries a massive flail. It also moves quite fast for its size, and attacks Kratos by attempting to pummel him with its flail. In order to destroy the monster, Kratos must first chip off all of its armor.
After weakening the enemy, Kratos can stab his way up on the beast, and climb it until he impales its shoulders. From there he then leaps over its head, twisting the chains and pulling back, thereby decapitating the Juggernaut. Killing it in this way will give Kratos some gold orbs, as well as a few green ones.
Juggernauts first appear in the Temple of Euryale, and then they are seen in the Hall of Atropos, the Lowlands Caves, the Arena of the Damned and the path to the Loom Chamber. They always are encountered in pairs or groups; and always fight alongside other creatures, such as Hades Fiends, Fates Guardians, Satyrs, Cerberi Breeder and Cursed Legionnaires.
There's also another very similar enemy, called Hades Juggernaut.