To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an escape cost), add any cost increases, then apply any cost reductions
Ancient Silver Dragon Anvil of Bogardan Body of Knowledge Choice of Fortunes Chronatog Avatar Curiosity Crafter Decanter of Endless Water Enter the Infinite Finale of Revelation Folio of Fancies Graceful Adept Kruphix, God of Horizons Library of Leng Marina Vendrell's Grimoire Mine, Mine, Mine
If youve seen some of the cards available in Modern, youll know that this gives you a disgusting amount of options, and doing it all in reaction to somebody attacking you or during their end step is rather silly
Such mischief
And if you do end up opting for Carmen in the Command Zone, I think youre going to want to lean into the ability to grow her large while making sure your deck runs plenty of free-equips, like Puresteel Paladin plus edict effects, too