In Torchlight 2, Runic Keys are special items that unlock unique content, such as new characters, areas, and game modes. These keys are hidden throughout the game world, and players can use them to access exclusive features that enhance their gaming experience. There are several types of Runic Keys in Torchlight 2, each with its own set of unlockables.
A common point of confusion is the "Runic Key" or "Serial Number." torchlight 2 runic key free link