Yenna, Redtooth Regent + Agatha's Soul Cauldron + Ashnod's Altar + Great Oak Guardian

Yenna, Redtooth Regent

Agatha's Soul Cauldron

Ashnod's Altar

Great Oak Guardian

How it works

1. Activate Great Oak Guardian using the Licid's ability by paying its activation cost, attaching Great Oak Guardian to Yenna and causing Great Oak Guardian to become an Aura.
2. Activate Yenna by paying 2 and tapping it, creating a token copy of Great Oak Guardian.
3. When the Great Oak Guardian token enters, it triggers, untapping all creatures you control and giving them +2/+2 until end of turn.
4. Activate Ashnod's Altar by sacrificing the Great Oak Guardian token, adding CC.
5. Repeat from step 2.

This ingenious loop relies on turning Great Oak Guardian into an Aura so that Yenna, Redtooth Regent can repeatedly copy it. Because the resulting token copy is an Aura, its entrance triggers Yenna to untap, while its own enter-the-battlefield ability untaps Yenna right back along with your other creatures. You can then feed the token into Ashnod's Altar for mana, while Agatha's Soul Cauldron waits in the wings to ensure you have all the color flexibility and activated ability support you need to keep the engine running smoothly.