Monsters are beings with the minds akin to that of humans. Every monster is often seen to be drastically different from each other, and like humans, they do human things as mentioned above. Monsters that cannot fight are referred to as creatures. Monsters from Badcadia, however, are known to have a feral mind, and therefore, are more hostile than those from Urd. Despite this, they were turned that way by Lux, the ruler of the outrealm. According to the prince, the Badcadian monsters are known to pose a threat against humans, and anyone who comes close to them unarmed will be slaughtered to death. Certain creatures that lack a human mind are non-sapient, and often live in the wilderness.

It is possible that a monster and demon can mate, although such practice is extremely rare. It is rumoured that a marriage between a monster and a demon can only happen once per three decades. So far, the only known monster/demon hybrid to exist in Urd is Renault of the Murgleis family.