Mine bonanza is unlocked at rank 39 of the free track of Luminous Night. Once unlocked, it can be equipped in the "Level Up Flairs" section of the cosmetic tab in the inventory.
Mine bonanza is a level up flair, meaning it activates when the player levels up. Once activated, a large amount of cubes that sound similar to Scatter Mines appear at the hero's feet and explode shortly after, leaving many glowing red squares floating in the air. After a short duration the effects disappear. As is the case with all flairs, mine bonanza's effects are purely cosmetic and have no other gameplay functionality.