Stellar Blade is a third-person action-adventure game set on a post-apocalyptic Earth. Players control Eve, an elite soldier deployed from an orbital colony to reclaim the planet from hostile creatures called Naytibas. The combat system emphasizes timing-based parrying and evasion, with skill gauges that unlock powerful attacks and buffs. The game features exploration across ruined environments, side quests from NPC survivors in the last human city of Xion, and a narrative with multiple endings based on player choices.

At the start of the 22nd century, the AI known as Mother Sphere was created to advance humanity, but the arrival of monstrous creatures called Naytibas drove humans from Earth. From their orbital sanctuary, the Colony sends elite soldiers to reclaim the planet. Eve, a soldier from the 7th Airborne Squad, is the sole survivor of a failed operation. Rescued by Adam, a scavenger who remained on Earth, she reaches Xion, humanity's last city. As Eve hunts Alpha Naytibas to locate the Elder Naytiba, she uncovers a disturbing truth: the "humans" from the Colony are synthetic beings called Andro-Eidos, created by Mother Sphere to replace the original humans, and the Naytibas are what real humans became in their attempts to evolve and fight back. Eve must decide whose side she is on as she confronts Adam's true identity and a choice that will determine humanity's future.