This one here is the help provided by PowerPyx:
- Set the amount of rounds to 2 in options
- Start a new ladder in Beginner (pick Scorpion)
- This can only be done on "The Pit" map in Ladder mode
- Once you reach "The Pit" (see video) do you see Santa Claus flying? (see video) If so you are on the right map. Instead of Santa Claus you will see a black shadow of a witch on her broom.
- You have to perform TWO flawless victories in a row
- Difficulty and fighter doesn't matter
- Pause the game and go back to player select if you fail
- You need to perform a Stage Fatality.
- After a loading screen Reptile will appear and also the trophy.
Thanks to PowerPyx for the video: