Xaranti

The Xaranti are a race of scorpion-like aliens, which have only appeared in Deep Blue.

Appearance
A pure Xaranti is described as being a combination of a spider, a scorpion and a bull. They are covered in quills and have pure-black eyes. They have eight spider-like legs and a scorpion-like tail (which injects a concentrated slime). They also smell like rotting fish. The individual Xaranti aren't especially bright and are instead controlled telepathically by the queen.

The Xaranti queen is a large, amorphous but intelligent blob. The queen is created and added to when the lesser Xaranti spit up a gel containing all their knowledge. This gel is added to the queen, who gains all the knowledge. The queen can take the forms of creatures the Xaranti have infected, but only for seconds.

Biology
Xaranti don't seem to reproduce normally and instead infect healthy members of other species.

The Xaranti start by spitting out a clear slime (probably related to the slime used to create the queen). The infection is water-borne and can be transmitted by swimming or eating infected sea-life. The infection begins with the host becoming more irritable and violent, and with them growing quills. Next, their eyes turn black and then the extra legs start to grow from their back. At this point, the host loses their mind and individuality and has become part of the swarm.

Oddly enough, the plague isn't biologically based, but instead mentally based. The slime makes the host believe they are supposed to turn into Xaranti. This means strong-willed individuals can last longer and very mentally powerful people can stop the infection.

Technology
Xaranti have no culture or technology, and instead steal other races. The Xaranti in Deep Blue were using a Morok Battle cruiser with their own adjustments.

Trivia

 * The Xaranti were apparently involved in a war with the Zygons, which is when their homeworld was destroyed.