Altar of the Brood
{1}
Artifact
Oracle Text
Whenever another permanent you control enters, each opponent mills a card.
Watch Out
ETB trigger, not a cast triggerRules Note
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.