Doppelgang + Mystic Sanctuary + Commander's Sphere

Doppelgang

Mystic Sanctuary

Commander's Sphere

How it works

1. Cast Doppelgang by paying 12, creating four token copies of Mystic Sanctuary, Commander's Sphere, and two other permanents that enter the battlefield untapped and can collectively tap to produce at least 2.
2. When the Mystic Sanctuary tokens enter the battlefield untapped, they trigger, putting Doppelgang on top of your library from your graveyard.
3. Activate a Commander's Sphere token's second ability by sacrificing it, causing you to draw Doppelgang.
4. Activate the four Mystic Sanctuary tokens by tapping them, adding .
5. Activate the three Commander's Sphere tokens' first abilities by tapping them, adding 2.
6. Activate seven of the other permanent tokens created in step 1 by tapping them, adding at least 7.
7. Repeat.

This high-mana loop uses a massive X-value cast of Doppelgang to manufacture a critical mass of tokens, leveraging Mystic Sanctuary and Commander's Sphere as the engine. When the Doppelgang tokens resolve, the influx of four Mystic Sanctuary copies triggers simultaneously to stack Doppelgang right back onto your library. You then crack a Commander's Sphere to draw Doppelgang straight into your hand while the remaining tokens and lands tap to generate the necessary mana to recast it. Because Doppelgang duplicates itself alongside everything else, you are able to exponentially scale your board state and resources every single iteration.