The following is a list of unnamed Overlookers.
Loquar's assistant []
This Overlooker alien was a member of Loquar's crew which stranded aboard a survey vessel in the Void in 2377 shortly after the USS Voyager.
After he and his superior joined Captain Kathryn Janeway's "alliance" they were able to enhance the technology in astrometrics. They introduced their new "spy" technology to Tuvok and were able to inform the captain about the "alliance" Valen formed with Bosaal.
He was able to escape from the Void as part of Janeway's alliance. (VOY: "The Void")
Observer []
This observer was the third member of the crew on a reconnaissance mission of the USS Voyager. (VOY: "Tinker Tenor Doctor Spy")
Overlooker []
The overlooker was Phlox's superior whom he reported to concerning his reconnaissance mission of the USS Voyager. When data of the events were transferred to the overlooker, he requested and received permission from the Hierarchy to launch an attack. He told Phlox he wanted no mistakes. When Phlox realized that what he saw were daydreams, he feared that the overlooker would punish him. He tried to convince the overlooker to change his mind about the attack, but the overlooker told him that if the information was not correct, he would inform the Hierarchy.
Phlox contacted The Doctor and warned him of the impending attack. The Doctor and Phlox were able to convince the overlooker to call off the attack due to the fact that Voyager had a photonic cannon that had destroyed the Borg. This was a fake weapon and used as a ruse. (VOY: "Tinker Tenor Doctor Spy")