Codie, Vociferous Codex | Voltaic Construct | Zirda, the Dawnwaker

Cards

({4} magic symbol) , plus enough mana to pay for the nonland card's mana cost minus ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) available.

Activate
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Codie by paying ({4} magic symbol) and tapping it, adding ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) .
Activate
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Voltaic Construct by paying ({1} magic symbol) , untapping
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Codie.
Repeat as desired, skipping step 2 on the final iteration.
Once you have an arbitrarily large number of
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Codie triggers, cast any spell by paying its mana cost, reduced by the ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) added in step 1.
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Codie triggers for each time you activated its ability.
Resolve the first trigger, causing you to exile cards from the top of your library until you exile an instant or sorcery spell with lesser mana value, and allowing you to cast that spell without paying its mana cost.
Repeat step 6 for each remaining trigger.
You may also repeat this combo for each instant and/or sorcery card in your hand as mana permits, and on subsequent turns.

Cast all instants and sorceries in your library with mana value less than spells you cast.