Seekers are strange creatures which live in the dimension which we know as chaos space. They seem to leech power off electronic appliances, as evidenced by one's arrival in the first book, and it is speculated that the first TimeRiders, save for Foster, were torn apart by the Seeker. However, an alternate theory suggests that instead of being killed by a seeker, it was instead a massive cascade of tachyon particles which drastically changed the units, aging them in seconds, and killing them instantaneously.
It has been suggested that these beings are the remnants of people who have used Time Displacement technology and somehow became lost in chaos space. Due to their hostility to anything that they see, people who come out of chaos space and end up mangled and fused together are regularly assumed to be subject to a successful seeker attack.
Seekers are unlike any creature from this realm. They show no signs of an exoskeleton or even an endoskeleton(an internal skeleton, like ours) and do not need to support their weight. Rather, they float, but exactly how they do so remains unknown. The Seekers have no known food source, but are able to keep themselves alive using electrical energy, as evidenced by the weakended seeker in the archway resorting to leeching off the electrical supply there. Seekers have no specified size, and can take whatever shape they wish, whether it be a cloud of particles, or even a dragon, a phenomenon witnessed by Liam and the team in the first TimeRiders book. Seekers appear to hold enormous amounts of thermal energy, as a successful attack from a seeker results in the victim's cuts being fused to other parts of his/her body. Seekers are not carbon-based lifeforms, and judging by their shape-shifting ability, they are not comprised of any known element at all. Rather, they could be comprised of pure energy, and could be invulnerable to any weaponry. Their only known weakness is that they slowly begin to fade away in our realm, requiring a constant supply of energy to keep themselves alive. This suggests that there is a constant and infinite supply of energy in chaos space, and the fact that some scientists who had lived during Edward Chan's time had hinted at "free lunch for everyone" supports this.