Collects Uncanny X-Men (1963) #132-140 & Uncanny X-Men Annual (1970) #4. The X-Men had fought many battles, been on adventures that spanned galaxies, grappled with enemies of limitless might, but none of this could prepare them for the most shocking struggle they would ever face. Jean Grey has gained power beyond all comprehension, corrupting her and transforming her into the Dark Phoenix! Now they must decide is the life of the woman they cherish worth the existence of the entire universe!