Since the ability says that you repeat its ability whenever you hit a land, youre guaranteed to get a free nonland permanent
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So, when Ardyn gets passed to you, it would make perfect sense to think that Boast is just the name of this insane activated ability that lets you stack your deck for one generic and a black per card
It also happens to be a core part of its strategy

Full Decklist Y'shtola, Night's Blessed G'raha Tia, Scion Reborn Alisaie Leveilleur Champions from Beyond Dancer's Chakrams Summon: Good King Mog XII Tataru Taru Thancred Waters Alphinaud Leveilleur Blue Mage's Cane Hermes, Overseer of Elpis Hraesvelgr of the First Brood Observed Stasis Eye of Nidhogg Fandaniel, Telophoroi Ascian Astrologian's Planisphere Reaper's Scythe Transpose Ardbert, Warrior of Darkness Emet-Selch of the Third Seat Estinien Varlineau Hildibrand Manderville Krile Baldesion Lyse Hext Papalymo Totolymo Urianger Augurelt Archaeomancer's Map Authority of the Consuls Cleansing Nova Final Judgment Archmage Emeritus Dig Through Time Rite of Replication Sublime Epiphany Torrential Gearhulk Crux of Fate Lethal Scheme Murderous Rider Baleful Strix Vindicate Void Rend Coveted Jewel Tome of Legends Choked Estuary Darkwater Catacombs Desolate Mire Drowned Catacomb Exotic Orchard Fetid Heath Glacial Fortress Isolated Chapel Port Town Prairie Stream Scavenger Grounds Shineshadow Snarl Skycloud Expanse Sunken Hollow Sunken Ruins Underground River White Auracite Sage's Nouliths Circle of Power Cut a Deal Lingering Souls Swords to Plowshares Hypnotic Sprite Into the Story Propaganda Bastion of Remembrance Exsanguinate Snuff Out Syphon Mind Arcane Signet Relic of Legends Sol Ring Talisman of Dominance Talisman of Hierarchy Talisman of Progress Thought Vessel Arcane Sanctum Ash Barrens Command Tower Contaminated Aquifer Demolition Field Evolving Wilds Idyllic Beachfront Path of Ancestry Sunlit Marsh Temple of the False God 3 Island 4 Swamp 4 Plains Franchise Magic: The Gathering Original Release Date August 5, 1993 Publisher Wizards of the Coast Player Count 2+ players Age Recommendation 13 years and up Length per Game Variable

And if youre jumping ship halfway through the draft, you may not have picked enough of those other cards to stick the landing