When a Xoid is crippled in battle, one of three things may happen to it. One: the Xoid is skilled enough to warrant the regeneration of its body. Two: the Xoid is taken and recycled. Three: the Xoid is abandoned and left to fend for itself. In cases where the Xoid is abandoned, the most often occurrence is that it dies, either from it's injuries or at the hands of the opposing force. Occasionally though, the Xoid survives and manages to get away to safety. Now, it should be noted that a Xoid will be abandoned only after extreme damage, such as the loss of major limbs or severe internal injuries. The Xoid mindset prioritises the whole, not the individual, thus a Xoid will be abandoned if the effort required to rescue and regenerate him outweigh the gains from his continued service to the Xoid forces.
If a Xoid is abandoned and manages to survive, its first goal will be to repair itself. Because of the similarities between Xoid anatomy and modern droids, the easiest way for a Xoid to repair itself is through the use of robotic components. Limbs and internal organs are thus replaced with robotic equivalents, often with enhancements and modifications from the original Xoid form.
The most likely event that happens next is the Xoid tries to return to service in the Xoid forces. They attempt to earn status enough to replace their robotic appendages with regenerated Xoid body parts. However, occasionally, the Xoid is unwilling to return to his native people. It is at this point when he becomes a Rouge Xoid.
Obviously, Rouge Xoids are rare. Of the Xoids that are abandoned, about 1% survive, about 1% of those manage to repair themselves sufficiently, and about 0.1% of those don't try to return to the Xoid forces. What causes these Xoids to strike out on their own is unknown. There have been many theories, most revolving about the Xoids considering themselves impure because of the robotic components. As far as is known, no undamaged Xoids have ever become rouges.
Rouge Xoids will always have some robotic body parts, often modified and enhanced for specialised use. The longer they are away from their Xoid brethren, the more their personality develops from the flat simple attitudes of most Xoids. They develop a wide range of goals, ideals, and motives and tend to spread outward through space. They retain the Xoid nomadic nature and rarely stay in one place for too long.