Millionaire Mystery Box is a thrilling and exciting video slot game based on the popular game show, Who Wants to Be A Millionaire. The game comes with amazing features and mechanics that make it stand out from other slot games in the market. Here are some of the features and mechanics of the game:

- The game is played on 5 reels, 3 rows, and 243 paylines, and you can place bets between 20p and £40 across all platforms and devices.

- In the base game, you will benefit from a Mystery Box mystery symbol that can land on any of the 3 middle reels. When you land at least one of these symbols, it will turn into a randomly chosen symbol, including the wild symbol and the scatter symbol. This will help to boost your winning chances and can trigger the free spins feature.

- You can gamble your winnings to double them or lose them all. The progressive wins are highlighted in 7 steps, and you can keep gambling until you hit the max win or lose.

- The free spins feature is the main attraction of the game, and you can trigger it by landing at least 3 scatter symbols on the same spin. You will initially receive 7 free spins and can climb the extra spin ladder on the left-hand side of the reels by landing more scatters. The ladder can award you up to 24 extra spins and a multiplier of up to 50x if you reach the eleventh and final step.

- The game symbols are true to the game show, and the purple gemstone is the highest value symbol, paying 25x for 5 on a payline. You also find the regular royal symbols of low value, and you need between 3 and 5 matching symbols on a payline to win.

- The game has medium volatility, and the maximum win is 12,000 times your stake, which can go up to £480,000 if you play with the highest possible stake.

- Millionaire Mystery Box is available to play on mobile and tablet, making it a convenient and exciting game to play whenever and wherever you are.

In conclusion, Millionaire Mystery Box is a must-try game for any slot enthusiast. With its mystery box symbols, free spins ladder, and high potential, there is never a dull moment in playing this game.