Codie, Vociferous Codex + Umbral Mantle + Biomancer's Familiar

Codie, Vociferous Codex

Umbral Mantle

Biomancer's Familiar

How it works

1. Activate Codie by paying 2 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 spell by paying its mana cost.
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/or sorcery card in your hand, and on subsequent turns.

This intricate mana-generation loop turns Codie, Vociferous Codex into an engine for infinite colored mana and arbitrarily large stats by pairing it with Umbral Mantle. Because Biomancer's Familiar discounts the creature's activated ability, the untap cost of Umbral Mantle is reduced so that Codie's tap-for-five ability pays for the untap while netting a surplus of mana. Each iteration of tapping and untapping adds another delayed trigger to Codie, Vociferous Codex, which eventually lets you rifle through your library and cast every single instant or sorcery for free.