If any of those face-down creatures have double strike or first strike, the ability will trigger once for each player dealt damage in each combat damage step
In fact, the card is barely played in any constructed format
It'll also let you tap your tappers more than once, like the next card
I think my default would be combat
Example Lists Mono Green Creature Based 24 Spells Llanowar Elves Fyndhorn Elves Elvish Mystic Joraga Treespeaker Noble Hierarch Skullclamp Rofellos, Llanowar Emissary Lotus Cobra Devoted Druid Explore Sylvan Advocate Satyr Wayfinder Tireless Tracker Rishkar, Peema Renegade Yavimaya Dryad Oracle of Mul Daya Garruk Wildspeaker Nissa, Worldwaker Verdurous Gearhulk Primeval Titan Walking Ballista Hornet Queen Crafterhoof Behemoth Decimator of Provinces 16 Lands Gaea's Cradle Treetop Village Rishadan Port 13 Forests Gr Ramp 23 Spells Search for Tomorrow Birds of Paradise Oath of Nissa Joraga Tree Speaker Arbor Elf Explore Sakura Tribe Elder Nature's Lore Sylvan Library Sylvan Caryatid Yavimaya Dryad Nissa, the Vastwood Seer Courser of Kruphix Den Protector Oracle of Mul Daya Polukranos, World Eater Garruk Relentless Nissa, Vital Force Primeval Titan Dragonlord Atarka Avenger of Zendikar Ugin, the Spirit Dragon 17 Lands Nykthos, Shrine to Nyx Myriad Landscape Kessig Wolf Run Tiaga Wooded Foothills Stomping Ground Raging Ravine Temple of Abandon 9 Forests These are just two fairly standard example lists
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