Knight of the Mists
{2}{U}
Creature — Human Knight
Oracle Text
Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)
When this creature enters, you may pay {U}. If you don't, destroy target Knight and it can't be regenerated.
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.