Enchantment // Legendary Creature — Dragon
Enchantment
When this enchantment enters, destroy up to one target creature.
At the beginning of your end step, if a creature died under an opponent's control this turn, create a Treasure token. Then if you control three or more Treasures, transform this enchantment.
Legendary Creature — Dragon
{1}{B}, Sacrifice another creature or artifact: Yiazmat gains indestructible until end of turn. Tap it.
This card's ability triggers when it enters the battlefield, not when it's cast. Effects that double ETB triggers (like Panharmonicon) work here. Countering the spell prevents the creature from entering, so the ETB won't fire.