You cannot simply rename a file. Hardcore saves have a flag inside the .gdc file. Using GD Stash, you can toggle the "Is Hardcore" flag. Warning: This is widely considered cheating, but useful if your hardcore character died due to a crash.
In the grim, aether-infused world of Cairn, where humanity clings to survival against eldritch horrors and undead legions, the path to power is traditionally paved with thousands of enemy corpses and countless hours of exploration. Crate Entertainment’s Grim Dawn , a celebrated action role-playing game (ARPG) in the vein of Diablo 2 , is defined by its punishing difficulty, deep character customization, and the sheer weight of its loot-driven grind. However, unlike many modern online "live service" ARPGs, Grim Dawn offers a fundamental feature that radically alters its social contract: local, unencrypted save files. This technical choice enables a widespread practice known as save file sharing. While often condemned as a form of cheating, a deeper examination reveals that save file sharing is a double-edged sword, acting as both a potential threat to the game’s intended challenge and a powerful tool for accessibility, build experimentation, and community longevity. Grim Dawn Save File Sharing