The Seeker was a reconnaissance device developed by the Xindi-Reptilians originally for use in the Xindi Civil War. It incorporated anti-gravity technology to fly and seek out enemies and then report back to its operator. Containing at least one techno-larva, the Seekers, like much other Xindi technology, incorporated biological components – so much so that a Starfleet scanner could actually mistake it for a Xindi bio-sign. Seekers could be prevented from detecting bio-signs using topaline ore.
The Reptilians attempted to use a pair of Seekers to locate Gralik Durr on the Xindi-Arboreal colony. One detected Enterprise captain Jonathan Archer, who destroyed it before it could return to the Reptilians. It fell to the ground, where a dark fluid seeped out of it. The other Seeker was struck by a phase-pistol hit fired by Enterprise lieutenant Malcolm Reed, but it continued to fly. It managed to escape and report in, but its scans were not definitive enough for its masters to reach any conclusions. Gralik later claimed he had destroyed the first Seeker because it was frightening tree scarabs he was hunting. (ENT: "The Shipment")
In the final draft script of "The Shipment", the sound of a Seeker approaching was described as becoming audible prior to the arrival of one of the devices. In the final version of the episode, though, the Seekers are shown arriving before any sound can be heard from them. The noise they made was described in the script as "a buzzing sound... a creepy, almost-insectlike drone", which was scripted to grow in volume as they approached.
In the same script, the actual Seekers themselves were initially referred to as "bio-mechanical drones" which were "suspended in mid-air by some kind of anti-gravity propulsion." The script went on to comment, "They have the same strange organic look as the 'quill-grenade' the Reptilians used in 'Rajiin'. These devices are clearly designed for search missions – they bristle with an array of spindly antennae and weird sensors." Although the destroyed Seeker is shown on screen as containing at least one CGI techno-larva, the Seeker's only visible contents referred to in the script was "a dark, oily fluid".
The Seekers were designed by illustrator John Eaves. He produced at least three concept sketches of a typical Seeker. The selected version received a star and a happy face drawn next to it.  The concept artwork for the Seeker can be seen here.