It is a single-player game. If you have already beaten Rebirth , Afterbirth , and Afterbirth+ , re-doing Greedier Mode with Maggie might feel like a chore. A Dead God file simply unlocks the "sandbox mode" so you can enjoy broken runs.
Whether you are a veteran seeking to avoid burnout or a curious player wanting to see the game's final secret (The "Number of the Beast" ending), the file exists as a shortcut through hell.
For the uninitiated, The Binding of Isaac: Repentance looks like a crude dungeon crawler about a crying child. For the initiated, it is a masochistic masterpiece; a rogue-lite labyrinth so deep, dark, and punishing that completing it fully is considered a lifetime achievement. At the pinnacle of this madness sits the Dead God achievement—the final, shimmering save file that proves you have done everything.