Bolas used the Immortal Sun to trap many Planewalkers on Ravnica after they had been lured there by the Interplanar Beacon to harvest their sparks. Chandra, Nissa, Saheeli, and Lavinia (plus Lazav) were tasked with shutting off the Immortal Sun. At New Prahv, they managed to do so after defeating Dovin Baan, which resulted in many Planeswalkers fleeing the plane. Jace had taught Chandra Azor's nine words that would shut off the Sun, which he had dug up from the sphinx's mind. Chandra managed to shut it off with the spell after being briefly possessed and overcome by its power.
Afterward, before the final battle with Bolas, they decided to reactivate the Immortal Sun to prevent Bolas from escaping. The Immortal Sun was returned to an inactive state at the very end after Bolas was defeated, but it was not destroyed in the event that it's needed again.
Associate maps for the Story line:
