Why did I just get 10 golden keys?
Just received 10 keys for Borderlands 2. I did not preorder the game. I own Borderlands, but I don't think that has any correlation to the golden keys in game.
Where did these keys come from?
There was an issue that would corrupt your profile, causing you to lose all your badass ranks. As part of the patch that fixed it, they also awarded all affected players 10 golden keys.
If you sign up at Gearbox Shift you will receive golden keys as a reward. If you use Shift codes you can unlock even more golden keys.
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