A triggered ability may read When/Whenever/At [trigger event], if [condition], [effect]. When the trigger event occurs, the ability checks whether the stated condition is true
Despite the time-gating, Shanna means business

Contents: 1 Aminatou, the Fateshifter 1 Adarkar Valkyrie 1 Boreas Charger 1 Conundrum Sphinx 1 Djinn of Wishes 1 Duskmantle Seer 1 Enigma Sphinx 1 Geode Golem 1 High Priest of Penance 1 Jeskai Infiltrator 1 Loyal Subordinate 1 Loyal Unicorn 1 Magus of the Balance 1 Mulldrifter 1 Night Incarnate 1 Ninja of the Deep Hours 1 Phyrexian Delver 1 Pilgrim's Eye 1 Serra Avatar 1 Sigiled Starfish 1 Silent-Blade Oni 1 Sower of Discord 1 Sphinx of Jwar Isle 1 Sphinx of Uthuun 1 Varina, Lich Queen 1 Yennett, Cryptic Sovereign 1 Yuriko, the Tiger's Shadow 1 Aethermage's Touch 1 Akroma's Vengeance 1 Aminatou's Augury 1 Army of the Damned 1 Azorius Signet 1 Banishing Stroke 1 Brainstorm 1 Cloudform 1 Commander's Sphere 1 Crib Swap 1 Crystal Ball 1 Devastation Tide 1 Dimir Signet 1 Dream Cache 1 Entreat the Angels 1 Entreat the Dead 1 Esper Charm 1 Lightform 1 Mind Stone 1 Mortify 1 Orzhov Signet 1 Ponder 1 Portent 1 Predict 1 Primordial Mist 1 Return to Dust 1 Seer's Lantern 1 Skull Storm 1 Sol Ring 1 Telling Time 1 Terminus 1 Treasure Hunt 1 Utter End 1 Arcane Sanctum 1 Azorius Chancery 1 Azorius Guildgate 1 Barren Moor 1 Command Tower 1 Dimir Aqueduct 1 Dimir Guildgate 1 Dismal Backwater 1 Forge of Heroes 1 Forsaken Sanctuary 1 Halimar Depths 5 Island 1 Isolated Watchtower 1 Jwar Isle Refuge 1 Lonely Sandbar 1 Meandering River 1 Mortuary Mire 1 New Benalia 1 Orzhov Basilica 1 Orzhov Guildgate 8 Plains 1 Scoured Barrens 1 Secluded Steppe 1 Sejiri Refuge 1 Submerged Boneyard 3 Swamp 1 Tranquil Cove 1 Aminatou, the Fateshifter 1 Adarkar Valkyrie 1 Boreas Charger 1 Conundrum Sphinx 1 Djinn of Wishes 1 Duskmantle Seer 1 Enigma Sphinx 1 Geode Golem 1 High Priest of Penance 1 Jeskai Infiltrator 1 Loyal Subordinate 1 Loyal Unicorn 1 Magus of the Balance 1 Mulldrifter 1 Night Incarnate 1 Ninja of the Deep Hours 1 Phyrexian Delver 1 Pilgrim's Eye 1 Serra Avatar 1 Sigiled Starfish 1 Silent-Blade Oni 1 Sower of Discord 1 Sphinx of Jwar Isle 1 Sphinx of Uthuun 1 Varina, Lich Queen 1 Yennett, Cryptic Sovereign 1 Yuriko, the Tiger's Shadow 1 Aethermage's Touch 1 Akroma's Vengeance 1 Aminatou's Augury 1 Army of the Damned 1 Azorius Signet 1 Banishing Stroke 1 Brainstorm 1 Cloudform 1 Commander's Sphere 1 Crib Swap 1 Crystal Ball 1 Devastation Tide 1 Dimir Signet 1 Dream Cache 1 Entreat the Angels 1 Entreat the Dead 1 Esper Charm 1 Lightform 1 Mind Stone 1 Mortify 1 Orzhov Signet 1 Ponder 1 Portent 1 Predict 1 Primordial Mist 1 Return to Dust 1 Seer's Lantern 1 Skull Storm 1 Sol Ring 1 Telling Time 1 Terminus 1 Treasure Hunt 1 Utter End 1 Arcane Sanctum 1 Azorius Chancery 1 Azorius Guildgate 1 Barren Moor 1 Command Tower 1 Dimir Aqueduct 1 Dimir Guildgate 1 Dismal Backwater 1 Forge of Heroes 1 Forsaken Sanctuary 1 Halimar Depths 5 Island 1 Isolated Watchtower 1 Jwar Isle Refuge 1 Lonely Sandbar 1 Meandering River 1 Mortuary Mire 1 New Benalia 1 Orzhov Basilica 1 Orzhov Guildgate 8 Plains 1 Scoured Barrens 1 Secluded Steppe 1 Sejiri Refuge 1 Submerged Boneyard 3 Swamp 1 Tranquil Cove Company: Wizards of the Coast Brand: Magic The Gathering Series: Commander 2018 Item Type: Deck Release Date: August 2018 UPC: 606583905994 Stock #: 268550 Our Guarantees to You, Our Valued Customer

Calix comes down earlier, its true, but having more than one of this effect in your deck isnt exactly bad
Green cards work for many archetypes (control decks, tempo decks, defensive decks)