Yenna, Redtooth Regent + Agatha's Soul Cauldron + Ashnod's Altar + Corridor Monitor

Yenna, Redtooth Regent

Agatha's Soul Cauldron

Ashnod's Altar

Corridor Monitor

How it works

1. Activate Corridor Monitor using the Licid's ability by paying its activation cost, attaching Corridor Monitor to Yenna and causing Corridor Monitor to become an Aura.
2. Activate Yenna by paying 2 and tapping it, creating a token copy of Corridor Monitor.
3. When the Corridor Monitor token enters, it triggers, untapping Yenna.
4. Activate Ashnod's Altar by sacrificing the Corridor Monitor token, adding CC.
5. Repeat from step 2.

This clever loop relies on Agatha's Soul Cauldron to grant Corridor Monitor's untap ability to Yenna, Redtooth Regent, though it utilizes a strange mechanical transformation to treat the Monitor as an enchantment. Once Yenna uses her tapped ability to churn out a token copy of that aura-fied Corridor Monitor, the token's entry triggers an untap of Yenna herself, while Ashnod's Altar stands ready to sacrifice the freshly made copy for colorless mana to fund the next iteration.