The Malediction is Magatsumi’s wartime crime, the thing Samura tried to kill by killing the men who won. Enten’s True Realm is Magatsumi’s death. Essay: Malediction. Blade: Magatsumi. War: Seitei War.
This page does not invent a first-blade name. The first Enchanted Blade is still unnamed after chapter 131’s listing. File: the first blade.