The Milestone Spin is a wheel of luck that lets you earn amazing rewards. Each time you reach a milestone after completing 100 levels, you will be able to spin the wheel of luck when it pops up. You will be able to see the Milestone Spin on the map after every 100th level.

If you are starting the Legends Arena, you will be able to spin your first wheel of luck after completing the 50th stage.

You can also find the Milestone Spin in the events section.