Grimm

The Creatures of Grimm, or just Grimm, are one of the five intelligent races that inhabit Remnant. The Grimm were originally created by the God of Darkness but they continued appearing thanks to the grimm pools.

They were described as "creatures of destruction" that lack a soul; hence and that they were unable to use Aura. Drawn to feelings of negativity - such as envy, sadness, loneliness and hatred - often congregating towards the source of these emotions. But reality is that like the other intelligent races they have a concience and the choice. They mostly attack small human villages or used to kill the travelers to warn the humans to get away from their reproduction territory where they keep their tribes. In other words they just try to protect themselves from the other races but like any other specie, they are able to feel and some of them can turn evil in the name of vengeance or ambition.

All of the first wave of Grimms were wiped out except for Damon who was strong enough to survive. As grimms were created to destroy, their first thought once they born is kill no grimms creatures but after few days, they adapt to the new reality and are against killing humans or faunus if it is not necessary.

History
The Grimm were created by the God of Darkness in order to destroy his older brother's creations of life. Eventually, the brothers ended their feud and both created Humanity, however, despite the younger god's involvement in creating Humanity, the Grimm were still left to roam Remnant and prey on them.

The Grimm have been locked in an existential war with Humanity for as long as can be remembered, seeking to destroy them and all of their creations in order to survive and eliminate their biggest threat. At first, it seemed as though they would succeed, as Humans did not have the strength to fight them. However, Humans discovered the power of Dust, and with it, the Grimm were driven back. During this time, Humans enjoyed a time of peace and soon formed their own Kingdoms, which grew to survive and prosper. However, this time would not last indefinitely.

While Grimm are moderally intilligent and organized, some Grimm are much more powerful that they have survived to live for hundreds of years. In that time, they have evolved and learned from their experiences fighting humanity. This leads them to exhibit restraint and the patience to avoid taking unnecessary casualties in futile conflicts; some of them accepted humanity and tried not to attack them to keep peace between both races but most of them stay close to humanity's borders, waiting for the opportunity to come where they can finally strike. Because of this, mankind is in ever-present danger, even in times of apparent peace.

The Grimm have also, for many years, disrupted land-based travel and communications between Kingdoms because they feared that if they were communicated they would start an organized massacre towards the Grimm they would lose because of their lack of resources. However after the Great War of Remnant ten years before the book begins, the invention and production of the CCT towers replace futile land-based communication systems with instantaneous wireless electronic messaging capabilities.

Additionally, the Grimm appear to be the predominant species in the world of Remnant as Humans and Faunus appear to be limited to four primary pocket settlements referred to as Kingdoms, which are guarded by Huntsmen, as well as several villages that exist with mixed success. Attempts by the Kingdoms to expand beyond their borders are often met with resistance, and even failure, such as the loss of an entire sector of the city of Vale to the Grimm.

Arise of the Beacons of Darkness
Apparently in times of peace, Salem made her first move in centuries to get the world peace she had dreamed of, the one that could only be achieved by domination. With the help of the Beacons of Darkness led by her adoptive son Duncan Crystal got to form a new empire called the Shadow Kingdom in the Darklands and in just 5 years they had the most advanced kingdom and the only one with acces to the Dark Cross Continental Transmit System created by Allan Crystal which worked with Satellites.

Also, the group Dark Redemption got a partial control of the kingdom of Vale, while the Reborn group succeded in taking control of a part of Atlas. Meanwhile the Fallen Fang got more influence in most part of Menagerie and Vacuo; the Covenant worked hard on the improvement of their forces and represented a great support to the Beacons of Darkness. Normally the Hot Road used is immunity to traffic weapons or anything the Beacons needed.

Modern Day
Today, thanks to Axel who acted as a bridge between the Grimm and the other intelligent races, Grimm stopped being massacred or studied and in return they stopped attacking the villages and kingdoms.

Thanks to the Beacons of Darkness' influence crimes and deaths had dropped drastically since everyone either respects or fear their new kings and authorities making it impossible for grimms to hurt the other races or viceversa.

The world is said to be in an unprecedented state of peace, there are no racial tensions or crimes in their perfect world, the immoral practices had disappeared, as well as agitation from rebel groups.

All the world is populated by Grimms since they are the major population of Remnant. Since the world peace was achieved and the Beacons of Darkness took control, Axel Grimm ordered that every school and academy should teach the grimm language as the second most common language.

Biology
The births of Grimm are emerging from black pools in the Dark Land. However, most of Humanity is unaware of the origins of Grimm. Ancient Human cultures believed the Grimm were animals possessed by evil spirits or even the tortured spirits of animals themselves. Further study has disproved this theory over time, however, due in part to the discovery of even more species of Grimm which have no animal counterparts, such as Creeps. With the discovery of new types of Grimm every day, scientists are left with more questions than answers.

Grimm come in a variety of shapes and sizes; the latter appears to be a factor of age. Grimm are very biodiverse as different individuals may be born with more or less size, armor, spikes, etc. They are said to be the only creatures without souls, thus being deprived of the use of Aura, but they make up for this with strength, durability and ancient knowledge. Some Grimm even have special abilities such as possession or usage of lightning and fire. Grimm are fearful to generally negative feelings such as sadness, hostility, anger and fear, mking them consider the ones to cause those feelings a threat to their tribes.

This behavior will even lead to them to join in on an attack in progress if the Humans being attacked begin to panic. Grimm typically form packs or other types of large groupings with other members of their own specific species. While some lone Grimm may stray from the pack for hours or even months, they will inevitably rejoin their group to continue their instinctive drive to hunt the people of Remnant and destroy any artificial creations associated with them.

The longer a Grimm lives, the larger it becomes, with species such as the Nevermore growing from the size of an average bird of prey to massive pterosaur-sized beasts after hundreds of years. Although Grimm have a more passive nature during their youth, older Grimm who have managed to survive their battles have the tendency to learn from their experiences and lead other grimms to the destruction of humanity. While sometimes requiring hundreds of years, the Grimm's accumulated experiences over the course of surviving their battles with man can cause them to begin exercising caution.

This perverse form of self-preservation can even lead them to avoid unnecessary conflicts altogether. Yet, despite this ability to learn, their instinctual hostility still remains, as shown by their preference to patrol the borders of Kingdoms for any weaknesses they might someday exploit. This demonstrates that for all their apparent intelligence, older Grimm simply use it as a means to become more effective in their singular drive and purpose of killing.

Grimm display enmity towards normal animals, and often hunt them for food, some grimms like Axel have stated that the human meat is awful compared to the normal animals. Humans and Faunus are the only races they attack on sight. Grimm can also choose not to eat, and it is commonly believed that they do not require sustenance but if they want to keep themselves strong and evolve faster they need the food. When a Grimm dies, their corporeal form evaporates, preventing detailed anatomical or biological studies. This also means that Huntsmen that kill for sport cannot stuff and mount Grimm bodies as trophies, making replicas instead.

There is also an as of yet-unknown method for granting human trait to grimm, as seen with the case of Axel Grimm who is a Grimm capable of transform in a human. And in the other side a mysterious method for granting Grimm anatomy to a human body. However, there are two critical weaknesses to those who undergo such a process. First, Aura cannot protect the Grimm component due to retaining the Grimm's soulless nature. Second, the graft user is vulnerable to the power of the Silver-Eyed warriors due to the Grimm's weakness to their power. On the other hand, such a graft user is afforded several abilities as well. One ability is the power to forcibly absorb and potentially assimilate the powers of a Maiden. Another is the power of elasticity; Cinder Fall was able to extend her Grimm grafted left arm several meters while still appearing to maintain physical strength. The graft user also appears to "bleed" from the Grimm component in the form of black smoke - the same way a true Grimm does.Given Salem's demonstrated ability to mutate the bodies of Grimm through magic, it is likely that magic is the primary means by which the graft is created and attached to the Human host.

Doctor Merlot's experiments
At some point, Merlot gained an unhealthy obsession towards the Creatures of Grimm, believing them to be a "superior species" due to their "unbridled raw aggression".

The corporation began performing experiments on Grimm, research which Merlot believed was vital to the future of Remnant. However, when they began running out of specimens to experiment on, they started attracting Grimm to the city in order to acquire more, with disastrous results. After the fall of Mountain Glenn, Doctor Merlot was presumed dead.

However, Merlot, in fact, survived the destruction of Mountain Glenn and transferred his operation to a highly remote island at an unknown location, and continued his experiments at his new secret laboratory, creating new forms of mutant Grimm using his serum, a glowing green substance.

Years later, Team RWBY would lead an investigation of mutated Grimm traced back to Merlot Industries, eventually arriving on Merlot's island. After Team RWBY infiltrates his laboratory and destroys his mutant Grimm, he self-destructs the laboratory.

Known Grimm that he conducted experiments on are Creeps, Beowolves and Death Stalkers. They were given powers like exploding/rebuilding and throwing bone spikes and can be recognized by glowing green skin.

Just some months later he was contacted by Duncan Crystal and Axel Grimm and was given the chance to join the Dark Redemption and continue with his experiments to create stronger grimms as long as they are volunteers.