Originally a mailaway offer via a coupon in the Pressman "X-Men Alert" board game and then eventually included with the box itself in a later release.
"Going Through the Motions"
Illyana is dying as Kitty returns to spend some time with her best friend, but that creates a rift between Jubilee and Kitty as Jubilee tries to get over it for the sake of Illyana. But in the end, there is nothing that Charles or Moira can do for her as she slips away into the darkness, leaving Jubilee to think that she is alone to deal with the loss, but she is part of a team and Jean lets her know of that.
Death of Illyana Rasputin (Magik).