In dealing with the emotional fallout from the murder of her sister, Frost travels to the mutant haven island of Genosha, where she teaches at a mutant school until a genocidal Sentinel attack kills most of the island's inhabitants; Frost survives due to the sudden manifestation of her secondary mutation: the power to transform herself into a flexible, near-invulnerable, diamond-like substance. After being rescued Frost joins the X-Men and takes on a teaching position at Xavier Institute. She mentors a group of telepathic quintuplets, the Stepford Cuckoos, who quickly become her prized pupils. Frost and the Cuckoos prove themselves when they help fight and defeat Charles Xavier's evil twin sister Cassandra Nova. As a member of the X-Men, Frost begins counseling Cyclops over his marital issues with Jean. She quickly develops feelings for him but Cyclops initially rejects her advances.