First revealed among the new game files included in the release of the Half-Life: Alyx Workshop Tools, the Jelly Blobber is a blue jellyfish-like creature that can float. Lacking any obvious eyes, it has several long tentacles at the front and underside of its body, several shorter feelers along its midsection, a fin along its top, a green and yellow sac at its bottom, and a thin tail. It appears to be a non-hostile entity that would harmlessly fly around areas in the Quarantine Zone that are overrun with Xen infestation. Little else is known about the creature as there are no remnants indicating where it was specifically intended to appear or what else it may have done.
The unused model contains three animations: an idle sequence in which it wobbles in place in a very jellyfish-like fashion and two placeholder sequences of it flying around in a circular path. Its entity options in the map editor indicate it was meant to fly along fixed paths. It has one associated particle effect named
xen_gnats_3.vpcf which depicts several small glowing Xen creatures floating around.
- Its design resembles Physalia physalis, it is a monotypic species of hydrozoan siphonophore in the family Physaliidae. It is usually found in the open sea in all the warm waters of the planet, especially in the tropical and subtropical regions of the Pacific and Indian Oceans, as well as in the Atlantic Gulf Stream. Its sting is dangerous and very painful. They go alone, not in groups.
- The possible behavior of the Jelly Blobber could be based on the animal itself.
- The Jelly Blobber is visually and conceptually similar to a cut enemy from the original Half-Life game known as the Flocking Floater. It is unknown if the Jelly Blobber was intended to be a spiritual successor to the Flocking Floater.