Xen Tentacle

The Xen Tentacle is a large alien creature from Xen that appears in Half-Life. Its scientific Latin name is Hypersuctor sensitiva, owing to its violent reaction to sound and vibrations. During the Black Mesa Incident, three of these creatures appeared in one of Black Mesa's rocket firing chambers.

Overview
The Tentacle's body appears to be a long, segmented green stalk with its head ending in a large blade-shaped appendage. While its head does possess an eye, it does not seem to respond to visual stimuli and has only been seen reacting to sound and vibrations.

When a Tentacle detects any nearby noise, it will lash out with its blade at the sound's source, swiftly butchering any living thing that treads through its lair without being completely silent.

The Tentacle cannot be killed by any weapon in the player's arsenal, but can be briefly stunned. It can also be distracted by utilizing grenades, throwing them afar and allowing the explosion to get the Tentacle's attention.