"<ref name="slush"></ref> Byrne created the characters Alpha Flight,<ref>Sanderson "1970s" in Gilbert (2008), p. 189</ref> Proteus,<ref>Sanderson "1970s" in Gilbert (2008), p. 190</ref> and Kitty Pryde/Shadowcat<ref> Also published in and </ref> during his run on "The X-Men".A new Brotherhood of Evil Mutants, led by Mystique, was introduced in the "Days of Future Past" storyline (#141–142, Jan.-Feb. 1981) in which a time-travelling Kitty Pryde tried to avert a dystopian future caused by the Brotherhood assassinating Presidential candidate Senator Robert Kelly.<ref>DeFalco "1980s" in Gilbert (2008), p. 200</ref> Byrne plotted the story wanting to depict the Sentinels as a genuine threat to the existence of the mutant race.<ref></ref> Byrne left "The X-Men" with #143 (March 1981).