Alopex was born an ordinary arctic fox outside of Fairbanks, Alaska. She proved herself deadly from an early age, serving as her pack's main hunter. She was both feared and respected by all other creatures in the area, save for a polar bear (who was the only being Alopex feared). This life continued until she was captured by a group of scientists attempting an experiment to bring other animals to human-level intelligence. In Alopex's case, the experiment was a success, first granting her human intelligence and then a human-like body. She was rescued from the laboratory by the Foot Clan's leader The Shredder and became an agent of the Foot Clan, believing it gave her life a purpose again.

In her first appearance, she attempted to trick the Turtles into showing her where their lair was so that the Foot Clan could find them and kill them. Fortunately, Raphael caught onto her scheme and fought her. She managed to get away though. After that, she can continually be seen fighting the Turtles at the Shredder's side.

Although Alopex served the Foot Clan faithfully, she still had some attachment to her old home and family. Seemingly aware of this, Shredder sent her back to Fairbanks while he had the forest burned down as a test of loyalty. Alopex attacked Shredder, although she quickly surrendered and professed her ultimate loyalty to the Foot Clan. However, comparing Shredder to the bear that had been the bane of her existence in her earlier life, she secretly swore that she would one day kill him.

During a fight between Shredder and Master Splinter, Alopex finally attacked her master. She did not succeed in killing him, however, and was stopped by Shredder's granddaughter Karai (who up to that point had considered Alopex an ally and friend).

Although injured, Alopex managed to survive and escape. She followed the Turtles, accompanied by April O'Neil and Casey Jones, to the home of April's parents, as they believed they were no longer safe in New York after the Foot had taken over the city's criminal underworld. Raphael was the first to notice her and attacked her, believing her to still be allied with the Foot. Raphael's brothers managed to stop the fight. After Alopex explained her situation, Splinter offered a truce with her. Alopex declined saying she did not need his or his sons' help, but she remained close to their new home. Alopex would later change her mind and joined the Turtles as a resident of the O'Neils. She even became friendly with Raphael, but this quickly changed when a group of Foot Assassins attacked the Turtles. Believing Alopex to still be loyal to the Foot Clan, Raphael attacked her. However, after she saved Raphael from being attacked by one of the Foot Assassins, he realized she was telling the truth.

Returning to New York thanks to a subliminal suggestion from Kitsune, she observed Angel Bridge, AKA Nobody, from a distance, until she enlisted her help in fighting Bebop and Rocksteady, who were getting into a fight with the Turtles and The Mighty Mutanimals. After Bebop and Rocksteady were defeated, Hob offered her a place in his army, but she refused, instead teaming up with Nobody to help keep the streets clean of crime.