to enable internet multiplayer, you likely don't need one. Modern digital versions of the game typically use account linking rather than a physical key. How to Access Multiplayer Without a Key

: These links often lead to surveys or "human verification" steps that trick you into giving away your email, phone number, or credit card information [1, 2]. Account Bans

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: Sometimes, the developers release items or codes for free through their official channels. Checking the official Torchlight II website or forums can be a good start.

For more information on item IDs and console commands, you can check the official Torchlight 2 wiki or community forums.