Yenna, Redtooth Regent + Ordeal of Nylea + Tiller Engine + Thaumatog

Yenna, Redtooth Regent

Ordeal of Nylea

Tiller Engine

Thaumatog

How it works

1. Activate Yenna by paying 2 and tapping it, creating a token copy of Ordeal of Nylea, then untapping Yenna and causing you to scry 2.
2. Activate Thaumatog's second ability by sacrificing the Ordeal of Nylea token.
3. The Ordeal of Nylea token's second ability triggers, causing you to search your library for two basic land cards and put them onto the battlefield tapped.
4. When the lands enter the battlefield, Tiller Engine triggers twice, untapping them.
5. Resolve the Thaumatog ability from step 2, giving it +1/+1 until end of turn.
6. Activate the two lands by tapping them, adding 2.
7. Repeat.

This clever loop relies on Yenna, Redtooth Regent duplicating Ordeal of Nylea to repeatedly harvest lands straight from your library. Because the copied Ordeal of Nylea is an Aura, its creation conveniently untaps Yenna to keep the engine going. Thaumatog serves as the necessary sacrifice outlet by munching away the enchantment token, which triggers the Ordeal's sacrifice ability to fetch two basic lands. Finally, Tiller Engine steps in to immediately untap those newly fetched lands so they can be tapped for the exact mana needed to pay for Yenna's activation cost.