Iroas's Blessing
Enchantment — Aura
Enchant creature you control
When Iroas's Blessing enters the battlefield, it deals 4 damage to target creature or planeswalker an opponent controls.
Enchanted creature gets +1/+1.
The blessing is not the strength itself, but the knowledge of how to use it.
Illustrated by
Theros Beyond Death#142CommonEnglishLegality
Rulings
Jan 24, 2020
If the creature Iroas’s Blessing would enchant is an illegal target by the time the Aura spell resolves, the entire spell doesn’t resolve. It won’t enter the battlefield, so its ability won’t trigger.