Missing Mythic Prisms from Overwatch 2 Premium Battle Pass

You can obtain Mythic Prisms through seasonal play by purchasing the Premium Battle Pass for the current season. As you progress through the levels of the Battle Pass, you will be able to unlock the Mythic Prism rewards. To see the list of unlockable rewards on the Battle Pass, open your Overwatch client, click on Battle Pass, and use the arrows to scroll through the levels of the Battle Pass. Generally you will find one Mythic Prism reward for every 10 levels of the pass.

If you have not purchased a Premium Battle Pass, you will not be able to unlock the Mythic Prism rewards unless you do.