These are the monsters used by Xaviax, normally invisible to those who lack Advent Decks or who have never passed through a mirror. They serve in grabbing and bringing the people Xaviax chooses into Ventara for his research and to obtain enough DNA samples for a machine to mass-transport the people of Earth to Karsh as slave labor to rebuild it. Xaviax creates them through unknown means, a mere hand wave seeming capable of spawning a new monster. Other than the Minions, none of their names are used onscreen, simply being called "Monsters". Their precise connection to the Riders' Advent Beasts isn't expounded upon, but it can be theorized that those Monsters were made by Eubulon the same way Xaviax made his.