Obsidian Howlers

The Obsidian Howlers are a unique species dwelling within the Gloomdepths of Shadow's Reach. Due to the nature of living in a cave system they have developed and extraordinary form of communication that frightens most explorers.
The howlers are quadrupeds, about the size of a wolf, but have scales instead of fur. The scales are obsidian-like absorbing the dim light of the Gloomdepths allowing them to blend seamlessly into their surroundings, this helps them ambush their prey. A single ridge of sharp, crystalline spines runs down their back and glows like the Ebonstone indicating an evolution to the exposure to Ebonstone.
The howlers communicate to each other by using various pitches and frequencies of sonic waves. To the untrained ear they sound like howling screeches that make one want to rip out their ears. In addition, not all animals can hear the full audible spectrum of these vocalizations and the howlers use this to their advantage when hunting. This unsual form of communication has adapted to the acoustic properties of the Gloomdepths. The lower frequencies can rebound and echo much further allowing the howlers to communicate over long distances, while the higher pitched frequencies are used for more localized communication. The low frequencies can be used to scare prey into their traps, while the high frequencies can allow them to communicate without being heard by the prey.
There are even rumors that the howlers can amplify their howls by channeling their crystal spine and shooting out powerful disorienting howls that can stun their prey and enemies. One should be extra cautious if being stalked by these beings and should try to wear any form of hearing protection available.