Codie, Vociferous Codex + Umbral Mantle + Zirda, the Dawnwaker

Codie, Vociferous Codex

Umbral Mantle

Zirda, the Dawnwaker

How it works

1. Activate Codie by paying 4 and tapping it, adding .
2. Activate Codie by paying 1 and untapping it, giving it +2/+2 until end of turn.
3. Repeat.
4. Once you have an arbitrarily large number of Codie triggers, you may cast any instant or sorcery by paying its mana cost, reduced by the added in step 1.
5. Codie triggers for each time you activated its ability.
6. 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.
7. Repeat step 6 for each remaining trigger.
8. You may also repeat this combo for each instant and sorcery card in your hand as mana permits, and on subsequent turns.

This ingenious loop centers around Codie, Vociferous Codex as the engine, turning its restriction of locking you out of permanent spells into a massive advantage by chaining its activated ability. By equipping Umbral Mantle, you gain an untap loop that would normally require significant mana, but Zirda, the Dawnwaker steps in to discount that untap cost down to just one mana. With Zirda's cost reduction, activating Codie, Vociferous Codex and using Umbral Mantle to untrap it allows you to generate infinite mana of all five colors and an arbitrarily large creature. Every single activation also triggers Codie's cascade-like ability, letting you cascade through your entire deck to cast every instant and sorcery for free.