New Mutants Origins: Magik - Magik Mini Series #2

Magik #2
Chris Claremont
John Buscema
Tom Palmer

Illyana runs away with Cat, the corrupted version of Kitty Pryde. What occurs is a great adventure and growth of the character as they assault Belasco's lair.

Uncanny X-men Omnibus volume 3 is available at most bookstores, ebay, and amazon.

https://www.amazon.com/Uncanny-X-Men-Omnibus-Vol/dp/078519922