You can tap them to create a Disenchant, Braingeyser, Terroir, Shivan Dragon, Regrowth, or Black Lotus, and then you can cast it, but you have to pay the cost for it

Aang, A Lot to Learn Advent of the Wurm Aerith, Last Ancient Ahn-Crop Champion Ajani Unyielding Ajani's Aid Ajani, Mentor of Heroes Ajani, Sleeper Agent Ajani, Valiant Protector Ajani, the Greathearted Alenni, Brood Recruiter Alert Heedbonder Alessos and Pras, Acrobats Almost Perfect Altar of Bone Ancient Spider Anthem of Champions Anurid Brushhopper Aragorn and Arwen, Wed Aragorn, Company Leader Arahbo, Roar of the World Arashin Sovereign Archon of Valor's Reach Arcus Acolyte Armada Wurm Armadillo Cloak Arming Gala Armored Wolf-Rider Arwen, Mortal Queen Asmira, Holy Avenger Assure // Assemble Assure // Assemble Atzocan Seer Aura Mutation Aura Shards Autochthon Wurm Banquet Guests Barkshell Blessing Baseball Bat Bast, Panther Goddess Battle for Bretagard Begin Anew Behemoth Sledge Belligerent Brontodon Bess, Soul Nourisher Better Than One Black Panther, Vanguard Black Panther, Wakandan King Bloomwielder Dryads Botanical Brawler Brightglass Gearhulk Brigid's Command Bronzebeak Moa Bronzehide Lion Buried in the Garden Burnished Dunestomper Burrowguard Mentor Butterbur, Bree Innkeeper Byrke, Long Ear of the Law Cadira, Caller of the Small Calix, Destiny's Hand Calix, Guided by Fate Call of the Conclave Camaraderie Captain Sisay Captain Sisay Captured Sunlight Captured by Lagacs Caradora, Heart of Alacria Catti-brie of Mithral Hall Cease // Desist Centaur Healer

We're trying to play at the casual table after all
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Because damage remains marked on a creature until the cleanup step or an effect removes that damage, nonlethal damage dealt to a creature may become lethal if you switch its power and toughness during that turn