During the early 20th century, the daughter of the villainous Deadly Ernest, young Jane St. Ives, was witness to her father accidentally killing her mother, an act for which she swore vengeance on him. To gain her revenge, Jane became Nemesis and created a sword using both science and sorcery. She first encountered the team of Canadian heroes Alpha Flight when team members Northstar and Aurora were battling her father. Using her sword, she sliced her father to pieces and, secure in the knowledge that her revenge was complete, disappeared. When her father was resurrected by the creature named Scramble and succeeded in killing most of Alpha Flight, Nemesis returned. She managed to keep Alpha Flight alive using the life force of Ernest's previous victims, and Puck used her sword to slay him once and for all. Nemesis was not seen for some time; she reappeared as leader of the second Gamma Flight, a new team sponsored by the Canadian government with the intention of replacing Alpha Flight.

The two teams were ultimately forced to work side by side, and eventually Gamma Flight was disbanded. Several members of Gamma joined with Alpha; however, Nemesis did not, vanishing again and taking her feral teammate, Wild Child, with her. After helping Wild Child reclaim his humanity by becoming the hero Weapon Omega, Nemesis was captured by the Children of The Night, a band of sewer-dwelling children that she had once led. Their new leader, Roc, sought to defeat Nemesis but with Weapon Omega’s aid she overpowered him. When the chaos entity Carcass was freed, Nemesis, one of the heroes summoned by Shaman, traveled to the land of the dead to destroy the creature.

Later, after the Alpha Flight members were captured by the alien Plodex race, Nemesis was forcibly recruited by Doctor Walter Langkowski, Alpha's Sasquatch, who injected Nemesis with nano-technology and attached a device to her spine in order to control her in an effort to rescue the original Alpha Flight team; she reluctantly agreed. After rescuing the original team, Nemesis agreed to stay with Sasquatch’s group, and has convinced him to free her from his control.