Millionaire Mystery Box is an online slot created by Big Time Gaming that is built round a 5-reel, 3-row format. This game is all about the gameplay. Features include a. Return to player. Mystery Box is a reel, line online slot game with multiplier, hold and a dice games theme you can play at 20 online casinos. Millionaire Mystery Box is a ways slot designed to deliver a game to suit every type of player. Millionaire Mystery Box has a slick land-based feel and. Game. Try Who Wants to Be a Millionaire Mystery Box slot online for free in demo mode with no download or no registration required. You need to match the magical symbols which are all scatters. Instead, this 5-reel slot offers an amazing ways to win. Try Mystery Box slot online for free in demo mode with no download or no registration required. Enjoy Ways to Win. %. . Return to player. To play the game. There are ways-to-win. Big Time Gaming video slot review of Millionaire Mystery Box that contains Free Spins ✓ Bonuses ✓ Wild and Scatter Symbols. It is straightforward and easy to understand. The Millionaire Mystery Box slot machine doesn't have traditional paylines. Developed in partnership with OG's sidekick Golden Hero, this slot will take you on an underground j ourney to a mysterious alchemist's laboratory with all the. This mystery box game is a super fun PowerPoint that you can use in any lesson, whether you are teaching online or in the classroom.