Cavalier of Dawn
Creature — Elemental Knight
Vigilance
When Cavalier of Dawn enters the battlefield, destroy up to one target nonland permanent. Its controller creates a 3/3 colorless Golem artifact creature token.
When Cavalier of Dawn dies, return target artifact or enchantment card from your graveyard to your hand.
Illustrated by
Core Set 2020 Promos#10pMythicEnglishLegality
Rulings
You may put Cavalier of Dawn’s enters-the-battlefield ability onto the stack without choosing any target. It will resolve with no effect. However, if you do choose a target and the target permanent is an illegal target by the time that ability tries to resolve, the ability won’t resolve. No player will create a Golem token. If the target is legal but not destroyed (most likely because it has indestructible), its controller will create a Golem token.