Cerian Monsters are one of the most common species on Ceres, and are extremely diverse in shape, form, Element and size. However, though they show many similarities with their demonic counterparts (and are even able to crossbreed with them), they do have some very unique traits to them. The first is that most Monsters have a default animal-like form, and are rarely able to shapeshift like demons commonly can. Those that are able to shapeshift are often more advanced than their normal peers, and are certainly very powerful in their world. Though these shapeshifters are often able to master their forms by the age of 5, it's definitely possible to force some of their animalistic traits out in their human-like forms via stress.
Monsters are often either soliditary or social creatures. Unlike demons, they care for their young a great deal, and will often keep their offsprings close until they find a Mate and move on. After the offsprings start their path to create a new family, however, they are rarely seen by their parents ever again. The few Monsters that dare to eat offspring during harsh times are often chased off by any and all Monsters that spot them; especially those within their packs. They are often marked before they are chased off to warn others of this trait.
The species that live in social groups or packs often enlist the help of their Clanmates to help them raise their young. As a result, the species as a whole tends to be very social and friendly, though that friendliness fades if their territory is invaded, or a hostile visitor comes along. To those they treat as Clanmates, they'll often protect them with their lives, even taking hits in place of their comrades. Many Monsters have the capability to become Companions, or even True Companions if they feel a close enough connection with another.
Almost all Monsters are very polite to people they view as "superior" to them. If they feel they'll be dominated in a fight, they'll treat that person especially well.
The few Monsters that can shapeshift are often much stronger and/or intelligent than their normal peers. Though they may physically be able to blend into a demonic place, their scent and animalistic behaviors often give them away. However, these shapeshifters are often treated very well due to their rarity. They're often able to gain a "True Power" form if they gain enough strength/energy. These forms are often much larger than their default forms, and can be a terrifying sight to behold in battle (or if their loved ones are threatened). Some of those with such powerful forms may even be able to house a few of their precious ones within a protective cavity they possess, much like True Form-blessed Demons that have internal pouches.
They're able to crossbreed with demons due to their ability to carry Magic Seeds. Unlike demons, they often have no trouble carrying them, and can often carry a great deal of them at once. They usually are built to be able to support one more child than they can have, just in case something happens (such as an orphaned Monster being adopted into their family).
Monsters only have 2 sexes (male and female). It seems if they produce offsprings with someone who has a rare or hard-to-find master Element, their children are much more likely to acquire these stronger features.
Monsters have no bias against any sex when it comes to the gender of their Mate(s). Like demons, males of the species also have baculum, excluding a few select monkey species. Some Monsters are also gaining multiple pouches thanks to the increase in genetic diversity that's been occurring on Ceres. As a result, much like the demons of Ceres, male Monsters are starting to be able to bear Seeds physically as well.
As a whole, Monsters are very keen on scent and the auras of others. As such, a majority of the species is able to see the aura of others, and often have terrific noses (even moreso than demons). Their hearing also tends to be very good, depending on the species. They're also often able to use magic, even those that don't shapeshift, and can be a definite threat in battle. In general, if one is on good terms with them, Monsters can make invaluable friends and comrades, especially those that have a pack mentality.
Unlike demons, Monsters aren't so restrained when it comes to making Mate bonds. However, they still have a restriction on how many creatures they can Soul Bond with, and most species of Monsters simply choose to be monogamous anyway (though they're decidedly more flexible if they're provided the opportunity to expand their circles in beneficial ways).