Two Faced Liar is a Mental Floor 4 Challenge Introduced in Series 2.
The Caretaker's explanation to the game:
"Meet Madame Deux Visage, the Two Faced Liar. To pass this challenge, the unfortunates must listen to Madame's reflection make statements. They must decide if they are true or false. If they get three right, they will pass. But get three wrong, and they will fail."