The Underworld Horde is a group of demonic entities summoned by Vigo to end a Russian war.
According to an old Russian folktale, a sorcerer from the West unleashed all the fury of the underworld to turn the tide of a war in Russia. Even Death was among the horde. The Undying Soldier captured Death with his Mystical Sack. Now invincible, the soldier drove the rest of the horde back to the underworld.