Sinking Feeling + Hex Parasite + Clever Conjurer + Chromatic Orrery

Sinking Feeling

Hex Parasite

Clever Conjurer

Chromatic Orrery

How it works

1. Activate Chromatic Orrery's first ability by tapping it, adding 5.
2. Activate Clever Conjurer by tapping it, untapping Chromatic Orrery.
3. Activate Clever Conjurer by paying 1 and putting a -1/-1 counter on it, untapping it.
4. Activate Hex Parasite by paying 2, removing the -1/-1 counter from Clever Conjurer and giving Hex Parasite +1/+0 until end of turn.
5. Repeat.
6. Once you have infinite mana, you may instead use Chromatic Orrery's first ability to draw infinite cards.

This loop relies on Clever Conjurer acting as the mechanical engine, using its tap ability to untap Chromatic Orrery for a net profit of colored mana while Chromatic Orrery smooths your color requirements with its mana-filtering passive. To keep the loop going without running afoul of the -1/-1 counter drawback on Sinking Feeling (which turns the Conjurer into an untapping creature), Hex Parasite steps in to devour that very counter for a tiny investment of life or mana. The result is an infinite loop that yields boundless colorless mana, which Chromatic Orrery can then filter into infinite card draw to close out the game.