[LaLaLand]

Mystery box appears in the living room with 12 keys in, 10 black, 2 white.

Pull a black key - you have the right to evict one housemate on the spot and gain (fake) "immunity to the final".

The two evicted housemates are then evicted but are informed they are to return for the final week of the series and are still eligible to win due to the fact they was no public presence involved in their removal. & on their return, the two housemates who chose to evict them will be immediately evicted themselves.

A bit sh*tty, but it could shake up the power-hungry members of the house and/or the two people who helped the two evictees get a pass to the final week.