Death Stalker

Deathstalkers are large, dark, scorpion-like creatures of Grimm.

The Emerald Forest, Pt.2
A Deathstalker appears within a cave in the Emerald Forest. Jaune Arc and Pyrrha Nikos walk into the cave, mistaking it for the forest temple. Jaune spots a large glowing object in the darkness and thinking it is a relic, tries to grab it. When he does, the object is revealed to be the glowing stinger belonging to a Deathstalker. This prompts the beast to act by breaking out of the cave and flinging Jaune back into the heart of the forest. Pyrrha prepares to battle, but determines that a retreat is a better course of action.

Players and Pieces
The Deathstalker follows Pyrrha all the way to the abandoned temple, which Blake comments on. It then knocks Pyrrha in front of the others and Yang comments how they can all die together. Ruby tries to take it on herself, but is forced to retreat, then pinned to the ground by a Roc and finally is only just saved by Weiss' intervention. The group retreats to the cliffside and Blake, Pyrrha, Jaune, Ren, and Nora attack it. Ren shoots at its tail, but isn't able to shoot it off before he is flung against a nearby wall. Jaune is the one that comes up with a plan to beat it, by recognizing that Ren had weakened the stinger's connection to the rest of the tail, and having Pyrrha throw her shield to cut off its stinger, then telling Nora to smash the stinger into its head with her hammer. The Deathstalker then falls down a large trench.

Appearance
Much like the other creatures of Grimm, a Deathstalker has a base black exoskeleton as well as white, bonelike plates upon its back with red detailing. One of the more prominent attributes is the glowing golden stinger on its tail. It also has two pairs of large claws that it uses to corner its enemies in front of its stinger. The Deathstalker found in the Emerald Forest has what appears to be moss or grass growing on it's claws and torso, possibly signifying that it had been laying dormant in the cave for a long time.

Abilities & Powers
Other than the obvious attacks using pincers, a bite and a sting, not much is known about its attacks as it is yet to perform any. Its stinger however appears to glow in the dark, though the exact purpose of this is not known (though it did serve as a lure for Jaune).

A Deathstalker is also very strong, as it was able to shatter the rocks around a small cave entrance in order to escape. It was also able to fling Jaune a considerable distance just using its tail. It also has what appear to be battle scars on its body, signifying it has been in some tough battles and managed to survive, indicating a large amount of battle experience.

It is also highly resistant to damage, withstanding Crescent Rose, Jade Dragons, and Miló's bullets with ease. It has also been shown to resist blades such as Crescent Rose and Gambol Shroud.

Trivia

 * The cave where a Deathstalker emerges from has old drawings of people attacking the monster with sticks and spears. This could signify that the monster had been in the cave since the original war with the Grimm.
 * This is supported by the creature's aged and battle worn appearance, which suggests that it's very old.
 * They are seen in the Opening sequence of RWBY, along with other various Grimm.
 * Deathstalker is also the name of a species of scorpion.