Codie, Vociferous Codex + Necrotic Ooze + Puresight Merrow

Codie, Vociferous Codex

Necrotic Ooze

Puresight Merrow

How it works

1. Activate Necrotic Ooze using Codie's ability by paying 4 and tapping it, adding .
2. Activate Necrotic Ooze using Puresight Merrow's ability by paying W/U and untapping it, allowing you to exile the top card of your library.
3. Repeat as desired, skipping step 2 on the final iteration.
4. Cast any spell by paying its mana cost, reduced by the added in step 1.
5. Necrotic Ooze triggers for each time you activated Codie's 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 nonland card in your hand as mana permits, and on subsequent turns.

By turning Necrotic Ooze into a one-man orchestra of cascading chaos, this loop leverages Codie, Vociferous Codex's activated ability to churn out a massive five-color mana reserve while stacking up deferred cascade-like triggers. Meanwhile, the inherited ability from Puresight Merrow lets you cleanly filter or exile away unwanted cards from the top of your library on demand using its untap symbol. The magic happens because Necrotic Ooze consolidates both disparate activated abilities into a single powerhouse, letting you repeatedly sculpt your library and build up a towering stack of delayed triggers before you ever cast your first actual spell.