According to IGN, there were six playable character for the Mortal Kombat X E3 build. Those characters include Scorpion, Sub-Zero, Cassie Cage, Kotal Khan, Ferra and D’vorah. The game takes place 25 years after the events of the previous Mortal Kombat. As you can guess by the names, some of the characters are descendents of previous Mortal Kombat characters
Different fighting styles are also returning to the game. Last seen in games like Mortal Kombat: Deadly Alliance and Mortal Kombat: Deception. However, you won’t be able to change your fighting style on the fly. Players choose which one they want before the match starts.
Characters are also able to run and transition look smoother during gameplay. Gameplay has been borrowed from Injustice, allow for stage interactions that was seen in the trailer. More videos and screen for Mortal Kombat X when they come in.