Death Stalker

Death Stalkers are large, dark, scorpion-like creatures of Grimm.

The Emerald Forest, Pt.2
A Death Stalker 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 of a Death Stalker. This causes Pyrrha to flee as the Scoripon-like Grimm begins pursuit, while Jaune hangs on to the stinger for dear life, screaming in fear. The creature then breaks out of the cave and flings 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 Death Stalker 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 'now we can die together'. Ruby takes it on by herself, but is forced to retreat when both the blade and rounds from Crescent Rose prove ineffective. She is then pinned to the ground by a giant Nevermore's barrage of feathers and is only just saved from the Death Stalker by Weiss' intervention.

The group retreats to the cliffside. They flee from the Death Stalker across a small bridge, but the Nevermore destroys it, isolating Blake, Pyrrha, and Ren from Jaune and Nora. Eventually Blake is knocked across the gap the beast created while Jaune and Nora join the battle. 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: recognizing that Ren had weakened the stinger's connection to the rest of the tail; he tells Pyrrha to throw her shield to cut off its stinger, then has Nora drive the stinger into its head with her hammer. This attack successfully kills the Death Stalker; its corpse falling into the abyss surrounding the cliffside.

Appearance
Much like the other creatures of Grimm, a Death Stalker has a black exoskeleton underneath several 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 a pair of large pincers that it uses to defend itself and grab/cut into its targets.

The Death Stalker found in the Emerald Forest has what appears to be moss or grass growing on its claws and torso, indicating that it had been laying dormant in the cave for a long time, thus also signifying its advanced age. This is further reinforced by the crude drawings made on the entrance to the cave.

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 appears to glow in the dark, though the exact purpose of this is not known (though it did serve as a lure for Jaune). However, the use of its stinger was only seen once, on Ruby, where it failed when Weiss froze its tail in an ice barrier, saving Ruby. It implies that the Death Stalker uses its stinger like any other scorpion, as a jab for poisoning its prey, but it is unknown what, if anything, lies in its stinger.

A Death Stalker is also very strong, possessing immense physical strength, as it was able to shatter the rocks around a small cave entrance in order to escape, and many trees of the Emerald Forest while chasing Pyrrha. 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. The Death Stalker also seems to have enough speed, despite it's size, as it was able to catch up to a fleeing Pyrrha, even though she had a head start.

It is also highly resistant to damage, withstanding bullets from Crescent Rose, StormFlower, and Miló with ease, having no effect at all. It has also been shown to resist blades such as Crescent Rose, StormFlower, and Gambol Shroud.

Despite its resistance to damage, the Death Stalker seems to be slightly affected by strong blows, such as Nora's Magnhild, where it was left disoriented a few times. Somewhat ironically, the only object shown to be capable of piercing the Death Stalker's cephalothorax is the Death Stalker's own stinger, which falls directly into the beast's head after being severed.

Trivia

 * The cave where a Death Stalker 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 is very old.
 * It is also possible that the armor of a Death Stalker grows stronger with time, as the creature has battle scars from previous conflicts but advanced weapons, like Crescent Rose, prove ineffective in damaging it.
 * The Death Stalker's glowing tail sting's initial function is very similar to the Anglerfish in reality and its own glowing appendage. Both use it to lure their prey to them via the light on the end of the appendage, before attacking and presumably killing them.
 * One of them can be seen in the Opening sequence of RWBY, along with various other Grimm creatures.
 * Death Stalker is also the name of a real species of scorpion.