Grimm

The Grimm are monsters introduced in RWBY's first episode, and inhabit various parts of Vytal. They are described as "creatures of destruction" and lack a soul; hence they are unable to use Aura.

History
The Grimm are said to have first appeared not long after the dawn of mankind. They set their sights on the early humans and sought only to destroy them and all of their creations. For awhile, 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 the humans formed their own kingdoms, which grew to survive and prosper.

Although the old kingdoms eventually faded, the world of RWBY currently still enjoys a time of peace. But this time won't last forever, as in the absence of light, darkness can return and the Grimm will soon make a resurgence.

Beacon Academy Initiation
The Emerald Forest As part of Beacon Academy's initiation, new students must team up in the Emerald Forest and fight their way to a northern temple. The students soon are faced with several different Grimm monsters. Ruby and Weiss are attacked by a large pack of Beowolves, but are forced to flee when Weiss' attack causes a fire due to Ruby's accidental interruption. Yang is also attacked, but by two Beobears that only manage to damage her hair, sending her into a blind rage as she defeats one of the bears. The other is quickly killed in one strike by Blake. Likewise, Lie Ren is attacked by two Basilisks, which are defeated through the use of his Aura.

The Emerald Forest, Pt.2 While searching for the abandoned temple, Jaune Arc and Pyrrha Nikos find a cave that they confuse for the temple. While exploring, Jaune accidently grabs on to the stinger of a Grimm scorpion. Pyrrha then runs from the cave and the monster follows her out, breaking down a wall to do so. Once outside, it flings Jaune unto the air and Pyrrha is forced to flee.

Types of Grimm

 * Beowolves
 * Beobears
 * Basilisk
 * Scorpius
 * Roc

Trivia

 * The name for the creatures of Grimm may be a reference to the Brothers Grimm or Grimm's Fairy Tales, a famous classic collection of German fairy tales compiled by the brothers.
 * After one of the Beobears is killed by Blake, it began to smoke. This could mean that when Grimm are killed, they will eventually just dissolve.
 * The shapes and swirls on Adam's mask are similar to the designs of the Grimm, possibly signifying some kind of connection between himself and the Grimm. It may all be an allusion to Adam representing the Beast of Beauty and the Beast.