Mystery Symbol
A placeholder symbol that reveals or transforms into another symbol after landing, with the revealed identity decided by the game's RNG.
Definition
A mystery symbol lands as a generic or covered tile and then reveals which real symbol it represents, often all mystery symbols on screen turning into the same one at once. The reveal is determined by the random number generator, not by anything the player does. When many mystery symbols convert to a single matching symbol, the result can be a large simultaneous win. This adds suspense to a spin, yet the reveal probabilities are set within the math so the overall return stays in the house's favour.
Worked example
Four covered mystery tiles land across the grid. On reveal, all four flip to the same high-value symbol, lining up with an existing symbol of that type to form a sizeable win.
Why it matters
For a learner, mystery symbols illustrate that reveals are random and predetermined, not influenced by skill or timing. For a professional, the reveal weighting is a direct control over how often the feature produces small versus large wins.