|Out of universe information|
- "The more someone told him not to do something, the more he had to do it."
- —Elizabeth Weir
Janus was a Lantean scientist who lived most of his life in the Pegasus Galaxy 10,000 years ago, doing what he could do aid his people in the final days of their war with the Wraith. Regarded as a brilliant thinker and inventor, he was also seen as somewhat reckless by his superiors, as evidenced by his obsession with perfecting time travel. He returned to Earth following the evacuation of Atlantis, but made several trips back and forth over the course of his life, assisting with the experiments of his protégé, Pandora, and rebuilding his time machine.
After lying in stasis for the majority of the time between the rise of the Wraith and that of the Tau'ri, he was stumbled upon by SG-1, and he agreed to use his resources to help in their fight against the Der'kal. Janus lived just long enough to pass on his knowledge to brief traveling companion Jason Carter before at last letting himself die, ascending to join his brothers and sisters at long last.
BiographyEditJanus was one of the most well-known and brilliant Lantean scientists, and his inventions were never orthodox advancements. He took great pride in creating out-of-the-ordinary technological marvels, most of which were either banned or frowned upon by the Lantean Council. He installed a time machine in one of the many gateships in Atlantis, and hid many of his controversial inventions and research (such as a component of the Attero device) in his secret laboratory. He also designed a personal cloaking device and made use of Intergalactic communication devices and Communication stones. 
When Major Sheppard and Dr. Zelenka were killed when a Wraith Dart destroyed the Time Jumper and crashed into Lantea's ocean, Janus was able to save Weir and became her advocate when she met with the Lantean Council. While he argued and defended Weir on her behalf that she should be allowed to return to her own timeline and prevent the Atlantis Expedition from falling into the same tragedy again, High Counselor Moros and Melia refused, and Moros angrily condemned his experiments, ordering the Timeship destroyed and the city to be evacuated. Refusing to allow the future Atlantis Expedition to walk into the same disaster she herself had faced, Weir pleaded to Janus to help her find a solution that would save the expedition from walking into the same disaster she faced with herself. Janus agreed and, after doing some calculations, concluded that manually rotating the Zero Point Modules sequentially every 3,300 years would allow slightly more power to be available when the city was visited by the Atlantis Expedition and Weir decided to stay behind in the city to perform the task. Janus programed a stasis pod to re-awaken Weir every 3,000 years or so to allow her to manually turn the ZPM's. He also programmed a failsafe-mechanism into the city should power drop to to such a critical level that the shield would fail and cause the city, not to be flooded. 
As Weir decided to stay behind, Janus himself decided to escape with the rest of the Lanteans to Earth with the hope that his efforts to save Atlantis for the future Atlantis Expedition would succeed, and was the last Lantean to leave Atlantis. Sometime after arriving on Earth he rebuilt his timeship, which would later be used to destroy a Goa'uld mothership and eventually retrieve a ZPM from Ra, which was later used to shield and save Atlantis from the Wraith attack.