Q1: What are the exact words Megumi says during the chant?
Megumi recites: "Furube Yurayura. Yatsuka-no-Tsurugi Ikaeshi Yatsuka-no-Tsurugi Datsuroku-shin General Mahoraga." In official English localizations, this is translated as: "With this treasure I summon... Eight-Handled Sword Divergent Sila Divine General Mahoraga."
Q2: Why didn't Megumi gain control of Mahoraga after Sukuna killed it?
Under the binding rules of the Ten Shadows Technique, external participants void the taming process. Because Ryomen Sukuna entered the ritual circle from the outside and delivered the finishing blow, the exorcism concluded without awarding Megumi control of the Shikigami.
Q3: How did Sukuna manage to tame and summon Mahoraga later in the story?
After taking control of Megumi’s body in chapter 212, Sukuna gained full ownership of the Ten Shadows cursed technique. Because Sukuna possessed astronomical cursed energy reserves and an overwhelming domain expansion, he performed the exorcism ritual privately off-panel and successfully tamed Mahoraga under his own commands.