Sisibi is a large, lush planet, and a wide variety of Monsters inhabit it. Though Sisibans are the most intelligent living animal, all Monsters on Sisibi possess some form of sentience and capability to use magic. Each Monster on Sisibi has an association to one of the five Elements. Many have a subtype as well, stemming from a certain combination of two core Elements.
Monsters have inhabited Sisibi for all of known history, presumably even before the native Sisibans emerged. Some are even more intelligent than Sisibans, and capable of communicating on a Sisiban level; some possess no apparent intelligence at all.
The largest and most powerful Monsters are known as Beasts. These incredibly ancient Monsters are the channelling points of all magic on Sisibi, and the centerpiece of the five kingdoms.
Some Monsters, such as the Procedumons, appear to come from a place other than Sisibi. It is a mystery as to the origin of these inorganic Monsters.
All Monsters on Sisibi eat a diet of "energy blocks" extracted from the planet's crust. These blocks provide enough energy to sustain a monster for an entire day.
Monsters are an integral part of life on Sisibi. To the Sisibans, Monsters function as laborers, advisors, sources of power, gods, and friends.
Almost every Sisiban has a few Monsters in their life, but the relationship between a Sisiban and a Monster is totally unlike that between humans and animals. Most Sisibans do not, and would never, "own" a monster. Monsters are considered free beings as much as Sisibans are; the only relationship a Sisiban would have with a monster is a mutually beneficial and consensual one. "Owning" a monster carries the same stigma as "owning" a Sisiban would.