Mystery Symbol
On the random spins the Rumble Row reel modifier will activate above the reels. This can award various features to the reel below it. The Wild Reel will land a full reel of Wilds. Double Trouble will sync the symbols on that reel with the reel before it. X2 Multiplier will award a x2 Multiplier to all wins from that reel.
When one or more Mystery Symbols land, a random symbol is selected from the Wild, medium or low win symbols, and all Mystery symbols transform into this symbol. The mystery symbol is the Golden Grimoire™, which is shaped like the infamous mysterious book that inspired the game.