In Mystery Heroes, players cannot select their own hero.
- Although players are still able to select their starting hero in the "Assemble Your Team" session, they will be randomly assigned a hero after and cannot switch off of it.
- They will also be assigned a random hero every time they respawn, with their ultimate charge being reset. It is possible that a player could respawn as the same hero they were when they died.
- If this occurs, buildable objects will remain (such as turrets), but the ultimate charge is still reset.
- Because of the randomly-assigned hero mechanic, hero stacking is allowed.
During the Winter Wonderland seasonal event, Mystery Heroes is changed to Winter Mystery. It plays identically to the standard, but the only maps available are King's Row (Winter) and Hanamura (Winter).