The Ilwrath are large, red, spider-like aliens with numerous appendages, many eyes, and pincer mandibles. As a species, they are psychopathically violent and religiously fanatical. They worship their twin dark gods, Dogar and Kazon, supposedly speak through the HyperWave Channel 44, which coincidentally is the channel the Umgah love to send their prank messages on.
Humans have many horror stories of the Ilwrath and the gruesome things they do to their prisoners of war, including dismemberment, evisceration, and other forms of torture meant to please Dogar and Kazon. After the Ur-Quan Hierarchy's victory in the First War, the Ilwrath planned to sacrifice all Human beings to their dark gods in a bloody ceremony, but the Ur-Quan Kzer-Za did not allow this, as it conflicted with the Path of Now and Forever.
The Ilwrath pilot the Avenger-class ships.
The Pkunk tell that the Ilwrath were once a species of supreme and absolute good, but they tried to become even more good, which caused them to "wrap around" the good-evil spectrum, resulting in the pure evil species now associated with the name Ilwrath. The accuracy of this tale is uncertain, due to the playful nature of the informants.
Details about the Ilwrath prior to their supposed transformation are unknown.
The Ilwrath are Battle Thralls of the Ur-Quan Hierarchy. Due to their zeal in battling other species, they are the backbone of the Hierarchy offensive. Along with the Spathi, the Ilwrath were commanded to enforce the restrictions placed on Earth, but around the year 2137 abandoned their post to satisfy their (and their gods') bloodthirst.
In the end of SC2, the Ilwrath met their doom fighting the Thraddash in a war which led to both race´s annihilation. Good Riddance.