Skullgirls 2nd Encore Upgrade is now on sale at Steam for $10.04 with it being 33% off. The upgrade includes: all DLC characters, all DLC character color palate swaps, a fully voiced story mode, challenge matches with unique conditions, Trial mode, and lastly survival mode. You can purchase the add-on here.
Note that this is DLC and will need the base game which you can find here for $9.99.