THE UNCANNY X-MEN #390

Beast has discovered a cure for the Legacy Virus. The catch: the first mutant to use it dies! After many ours of laboratory work Beast emerges with a cure for the Legacy Virus. He made the cure from the codes he deciphered from Moira's notes on the virus. Xavier, Cecelia Reyes, Gambit and Wolverine congratulate Beast, who explains to them how the cure works. However, Beast and Cecelia realize that the cure can only be released after its host uses his or her power, which will then kill him or her. Beast stores the virus in a cabinet and goes an plays basketball with Gambit and Wolverine to clear his head. While the three debate on how they should be living their lives as mutants, Xavier enters the game. Inside, Cecelia senses something wrong with Colossus, who tells Cecelia all about his dead sister, Illyana. She realizes what he is going to do but is knocked out by him before she could stop him. He takes the virus and says "I'm coming home Snowflake" and injects himself with the cure and uses his powers one last time. She tries to find a pulse but ot no avail the long time teammate of the X-men is reunited with his family and baby sister. — Description from Comic Vine community (comicvine.gamespot.com).