Habitat: Freshwater. Marshland.
From a distance a freshwater cnidarian-girl looks like a pretty young woman in a long summer dress. They are normally found staring wistfully out across small bodies of water in picturesque wild spots.
The 'dress' is a thin membrane of elastic jelly that serves to hide the cnidarian-girl's lower body. Beneath the waist their body consists of a ring of thick tentacles that are used to both raise and support the upper torso, and restrain prey while the cnidarian feeds. Hanging down from the centre of the ring of tentacles is a specialised feeding tube.
The structure of a cnidarian-girl's body appears to be comparable to Earth-based cnidarians—hence the name—although they are considerably more complex. Their mostly liquid insides are held in by a strong membrane of semi-transparent jelly. While their skin colour comes in a variety of hues from yellow to green to muddy browns, they are capable of changing it to opaque pink for short periods of time in order to mimic human flesh.
The cnidarian-girl lures prey to her through an airborne pheromone that also massively raises the libido. Once the target comes within range the cnidarian-girl stings and immobilises them with a powerful paralysing agent injected through the skin by nematocysts located in her tentacles. With her prey immobilised, the cnidarian wraps her tentacles around them and begins to feed.
As with other HSIOs, cnidarian-girls feed on sexual fluids. Their body secretes a toxin that triggers the over-production of sexual fluids at the expense of all other biological functions. This toxin is absorbed through the sexual organs and requires the ejaculate of her prey to activate it. If her victim is male the cnidarian-girl ingests their penis with her soft feeding tube and uses this to stimulate them to ejaculation. If she has caught a female, the cnidarian turns the lower third of her feeding tube inside out and inserts it into her captive's vagina. Once her feeding toxin takes effect the cnidarian-girl slowly drains her prey of all their fluids.
Like their Earth equivalents, cnidarian-girls have soft, fragile bodies. Aside from their pheromone lure and paralysing sting they have little fighting ability and if threatened they will contract down to a ball, with the outer tentacles folding back up over their vulnerable upper body to protect it.
The pheromone lure is the main danger. Soldiers should stay together at all times and always be on the lookout in case one of their squad-mates starts showing signs of being under the influence.