Oko

This unidentified bat creature is something found by Jake Muller and Sherry Birkin while in an underground cavern in Edonia, trying to avoid the Ustanak.

Biology
The creature is very small and mobile, flying on two wings that closely resemble those of a bat. The primary feature is several glowing tumors on their body. When they are solitary and away from danger, the tumors are colored a bright blue. However, when they sense something nearby, the tumors suddenly turn red and they let out a loud, piercing shriek akin to a siren.

Gameplay
These bat-like creatures work in advantage to the Ustanak in the underground cavern of Edonia while Jake and Sherry are trying to avoid him. They project a bright blue color from the tumors on their body when left alone, but if anyone gets within range of the blue light, the creature will take notice. It will react by shrieking - alerting the Ustanak in the presence.

Strategy
It is likely that shooting these creatures is unrecommended as the sound could draw the attention of the Ustanak while it is hunting for you. Wait for an opening, observe its moments and run up behind it while its light is turned away. You'll be prompted for a contextual attack that will instantly smash and kill the creature. It does not seem as if running will alert this creature to your presence.