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The subject matter of this article contains in-development information that was cut from the final version of an official and/or canonical source and appears in no other canonical source. It may also contain incomplete information since not all cut material is publicly known.
The Panther Eye, also known as Panthereye, is an alien enemy cut from Half-Life. It comes in two versions: a blue-colored, which was created first, and a red-colored. While not in the retail game files, the source files of the red version can be found in the Half-Life SDK files, where its folder bears the name "Diablo". Both the blue and red versions can be found in the leaked Half-Life Alpha.
Like many of the Xen creatures, it has a single eye and is overall very similar to the Vortigaunt. Originally created for Quiver, it was first called "Sound Dog". This theme relates to the Houndeye, who bears a similar name.
 Behavior and skills
Of the size of a panther, it was to throw its victims on the ground and attack them somehow with its mouth and some sort of beige tongue located behind its chin (as seen in the red version), while blocking them with its paws. It was also to slash and push its victims with the claws of its upper paws. The creature was to run very fast, making it a very efficient opponent, and waving its tail while being idle. Other animations see it crawling on its belly to avoid being noticed. Overall, its behavior was to be more or less like a panther or any feline animal from earth, hence its name.
The blue version has compound eyes, likely allowing the creature to see with a very large view angle.
The leaked Half-Life Alpha contains 4 Panther Eye sounds, used for when it is idle. It consists mostly of high-pitched groaning sounds (reminiscent of the "Sound Dog" concept) and undetermined noises.
 Behind the scenes
According to "Skeletal Animation.txt", a text document in Half-Life Alpha, the Panther Eye was to have a tongue, and was to be animated using vertex animation. The tongue can be seen in a screenshot included along with the document. There is a version of the tongue animated using skeletal animation used by the red Panther Eye. The Gargantua also appear to have a similar tongue, which is used in several animations, and is hard to see because of its placement.
 In modding
 List of appearances
- Half-Life 1997 Teaser (First appearance) (Non-canonical appearance)
- Half-Life SDK (Non-canonical appearance)
- Half-Life 2: Raising the Bar (Non-canonical appearance)