The Mortal Kombat Season Pass is a discounted DLC package exclusive to the Xbox 360 platform. Once the pass is downloaded, it grants the player to download the first four DLC characters for the price of 1200 MS Points or $15. Buying all four DLC characters would be $20 so buying the pass would make one character free. This is most likely done due to the PS3 version of Mortal Kombat having an exclusive character in Kratos whereas the Xbox 360 version doesn’t have one.
Once you have the Season Pass, download the characters through the game instead of Xbox Live Marketplace. If you try to get them through Marketplace, you will have to pay for the characters. To get the characters in game go to “Extras” and then “Downloadable Content”.
This offer is available for a limited time only, so be sure to download it before it’s gone.