Procedural Missile Strike

When Procedural Missile Strike enters the battlefield, destroy all token creatures.
At the beginning of your next step, destroy all creatures with a converted mana cost of 1. At the beginning of your next step after that one,
destroy all creatures with a converted mana cost
of 2. Repeat this process until the most expensive creature at the time of playing Procedural Missile Strike has been destroyed; then exile Procedural Missile Strike.