Yeah, those are HIDDEN CHARACTERS, you can only unlock them by:
1. Make a profile
2. Earn Koins from Arcade mode, or Konquest mode
3. Now visit the Krypt, and try to unlock the right coffins that have the Kombatants in it.
Cyrax: CN 3003 Platinum Koins
Drahmin: UR 6500 Sapphire Koins
Frost: IV 208 Ruby Koins
Hsu Hao: MW 3317 Jade Koins
Jax: SA 3780 Ruby Koins
Kitana: KI 2931 Sapphire Koins
Nitara: TI 4022 Gold Koins
Raiden: XG 3882 Jade Koins
Reptile: LL 3822 Gold Koins
If any of those are wrong, they're most likely in the coffins with spotlight on them. (You'll know what I mean when you get there)
There are also 2 others, but you have to beat Konquest with every character to unlock them. To play as Mokap, you must highlight Cyrax, hold down and push START, to get Blaze, highlight Raiden, and hold Down and push START