Cylla Markham was a charter airline pilot assisting two former members of the team of superhuman mutant adventurers known as the X-Men, Banshee and Forge, in finding the whereabouts of their teammates. Her plane was shot down by the mutant brother and sister assassins known as Fenris, who had been tipped off to Banshee's plans. Seriously wounded, Markham was taken to a hospital in Athens, Greece. There, she was approached by Donald Pierce, the renegade White King of the Hellfire Club, who offered to transform Markham into a cyborg in exchange for her services. Markham agreed, and was augmented by Pierce into becoming the newest member of his team of cyborg assassins known as the Reavers. Cylla, as she came to call herself, was dispatched by Pierce to Tokyo, Japan to kill the feral X-Man named Wolverine, but was defeated by the combined efforts of Wolverine's allies Yukio and Jubilee.

Later, the Reavers were seemingly destroyed by giant robotic Sentinels summoned from the future by the time-travelling mutant Trevor Fitzroy. Cylla, who was in the midst of a cybernetic upgrade to become Pierce's new Skullbuster, saved herself and her fellow Reaver, Lady Deathstrike, during the Sentinel's attack.

Cylla eventually came to ally herself with the androids Albert and Elsie Dee and the energy-vampire known as Bloodscream who were seeking the whereabouts of Wolverine. She was killed when Bloodscream drained her life essence to feed his vampiric need for energy.