Nightmarchers

When Nightmarchers enters the battlefield, each opponent chooses any number of untapped creatures they control and taps them.
Return all Equipment attached to those tapped creatures to their owners’ hands.
Then, for each creature that wasn’t tapped this way, if its mana value is less than X, destroy it.
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"Kapu! Moe!" — The cry that splits the night. Prostrate, or perish.