The Ultimate Season 3 Bundle! Get early access to fighters! Includes 8 new fighters - including Rash from Battletoads, Arbiter from Halo, Kim Wu, and Tusk! Includes VIP Double XP Booster, 8 retro costumes, accessory sets, bonus character colors, and 18,000 KI Gold. Rash, Arbiter, Kim Wu, and Tusk available now - all other content to be released over the season.
Source: https://store.xbox.com/en-US/Xbox-One/DLC/Killer-Instinct-Season-3-Ultra-Edition/c71b9678-12bb-4986-b202-0efeff63da19
Looking forward to this, can't find the standard edition yet.