19 cards where the card is tagged “cost-reducer-activated-ability”

Agatha of the Vile Cauldron (Wilds of Eldraine #199)
Arms Scavenger (Alchemy: Innistrad #35)
A-Silver-Fur Master (Kamigawa: Neon Dynasty #A-236)
Auriok Steelshaper (Mirrodin #4)
Biomancer's Familiar (Ravnica Allegiance #158)
Blossoming Tortoise (Wilds of Eldraine #163)
Convergence of Dominion (Warhammer 40,000 Commander #154)
Embalmer's Tools (Amonkhet #227)
Fluctuator (Commander 2020 #241)
Forensic Gadgeteer (Murders at Karlov Manor #57)
Heartstone (Stronghold #134)
High Troller (Mystery Booster Playtest Cards 2021 #54)
Kemba's Outfitter (Alchemy: Phyrexia #2)
Power Artifact (Masters Edition IV #57)
Silver-Fur Master (Kamigawa: Neon Dynasty #236)
Tezzeret, Betrayer of Flesh (Murders at Karlov Manor Commander #120)
The Dining Car (Doctor Who #578)
Training Grounds (March of the Machine: The Aftermath #9)
Zirda, the Dawnwaker (Ikoria: Lair of Behemoths #233)

It is the moment of discovery, the triumph of the mind, and the end of these results.