In an alternate dimension, the Ancients suffered from a terrible plague that devastated their population, who created a Quantum Mirror for some of their number to escape to another dimension. With their civilization collapsing, they attempted to create a second generation of their kind by seeding Human colonies in the galaxy. However, these colonies themselves were ravaged by the plague, which led to both the Lanteans as well as their successor race facing extinction. Thus, in desperation, the Lanteans sought to create a race that would serve as their successors and began experimentation on the Iratus bug. In a controlled setting, they genetically engineered the Iratus bug to be combined with Human DNA, with this resultant race being bred not to feed off sentient beings. Thus, the Eidolon were created, who were their reality's version of the Wraith, though were a more benevolent as well as peaceful species that did not have the need to feed on sentient beings.
In time, the Lanteans perished and left the Eidolon to develop on their own, though their final act was providing the Ancient Technology Activation gene that allowed them access to Lantean technology. This race developed much of the physical features of the Wraith with their kind consisting of males, females as well as Queens though they lacked the drones. Furthermore, they retained telepathic abilities though they lacked the means to be sensed by Wraithkin. They came to hold great respect for and even revere the Ancients, who they called the Creators. With their society developing, the Eidolon formed pronounced Human behavioral characteristics. As they developed, they managed to create a mixture between Wraith and Ancient technology. This allowed them to create advanced scientific vessels with sensors able to pierce through cloaks. They also have beaming technology that is more similar to the Asgard transporter than a Wraith transporter in design.
Though the Eidolon were evolved to remove the need to feed, there were some among their kind that struggled with this instinct. These individuals were known to feed on other sentient beings, be it a child or sibling, whereupon they were labeled as criminals. The Eidolon did not know where this instinct came from, with them debating whether it was a psychological element or a genetic one. They came to the conclusion that the Creators had created their kind but had not removed the instinct to feed, and thus searched for a means of perfecting the process. By the time of the Atlantis expedition, the Eidolon discovered a Quantum Mirror over a moon linking their reality with the mainstream one. Under the leadership of a Queen, she decided to send her daughter Trishen through the Stargate styled Quantum Mirror to investigate the other side. Wearing an environmental suit, she met with Lt. Colonel John Sheppard's team who initially believed her to be part of an elaborate Wraith trap. At this time, a Wraith scout ship arrived which forced Sheppard to work with the Eidolon in fighting the Wraith whilst working to destroy the Quantum Mirror. Using a makeshift bomb, Sheppard's team and the Eidolons were able to destroy the scout ship. One of the Eidolon, Edane, gave into the instinct to feed, but was killed by Trishen who explained what had happened along with the Eidolon's initial hope that the Atlantis team might know something to help them. As the Eidolon left, taking with them some Wraith bodies in hopes that they possessed the answer they were looking for, the Atlantis team returned through the Mirror as it was destroyed and were rescued by the Daedalus. (SGA: "Entanglement")