Channel Fireball - Metalwork Colossus plus Paradox Engine, Witch's Oven, a mana rock, and a bunch of other artifacts gives you infinite mana. From there, Karn can fetch Aetherflux Reservoir to finish
Combo Crash Course: Cat-Oven - Card Kingdom Blog
Metagame Monday - Top 10 Cards to Beat Cat Oven Decks • MTG Arena Zone