When Rachel Summers landed in the apocalyptic future ruled by Apocalypse, she knew she had to find a way to ensure that this future would never come to pass. Her plan to thwart Apocalypse's ascension dealt with protecting her brother, Cable, in the main timeline.
Protecting Cable was a priority because his powers should rival her own and he could stop the ascension and ensure a brighter future. In order to accomplish these lofty goals, Rachel sent someone back in time to protect baby Cable at a critical junction. The person's name was simply Askani, and she forsook her body to travel in back in time as a being of energy. The threat to Cable involved an attack by Apocalypse (as recounted in the Endgame story arc), but Askani was too late. Baby Cable was infected with a techno-organic virus, a terminal disease that had no cure in the present timeline.
Askani was created by Chris Claremont, Jim Lee and Whilce Portacio and fist appeared in X-Factor Volume 1 issue 66 (1991).
Major Story Arcs
To make up for her tardiness, and to enable Cable to still be the "Chosen One," Askani offers to take Cable to the future to cure him. This causes Cyclops, Cable's father, severe distress, especially since Askani tells him that he will never see his son again. Cyclops ultimately lets his son go in hopes that the future could cure him. Cable would eventually be saved, but Askani would not survive the trip back to the future.
A Second Askani, a Second Trip
The Clan Askani once again senses a threat to the Summers family when Cable's body is inhabited by Stryfe's mind. The Askani worry that Scott Summers and Jean Grey would be targets of Stryfe again (as was the case during the X-Cutioner's Song) and send another member to protect the family. Again, the person calls themselves Askani (though a different person) and, again, Askani has forsaken her body to travel as a being of energy.
Where Askani was simply too late the last mission, Askani this time isn't even able to begin her mission, as Tyler Dayspring, the errant son of Cable, captures her energy signature and holds her captive. His plan isn't to allow Stryfe to kill Cyclops and Jean Grey, but rather to allow Stryfe to inhabit his father's body so as to exact revenge on both men at once. Capturing Askani is merely a way to make sure that nobody meddles in his plans. Askani's imprisonment, however, serves as the catalyst to undoing Tyler's plans.
Tyler's mutant powers include the ability to tap into someone's psyche and project the emotions of the person's memories. Askani holds the truth to Tyler's past, the revelation of which only further confuses the man. Stryfe (in Cable's body) finds the two shortly thereafter and obliterates Askani's energy form. Fortunately, Charles Xavier and Jean Grey are able to harness some of that energy and use it to talk sense into Stryfe by showing him the truth about his past. Once Stryfe releases his hold on Cable, Askani's energy form supposedly dissipates, resulting in a total death.