Rat King, Verminister + Intruder Alarm + Belonging + Viscera Seer

Rat King, Verminister

Intruder Alarm

Belonging

Viscera Seer

How it works

1. Cast Belonging by paying 5.
2. When Belonging enters, it and Intruder Alarm trigger.
3. Resolve the Belonging trigger, creating three 1/1 Shapeshifter creature tokens with changeling.
4. When the Shapeshifters enter, Intruder Alarm triggers three times. Resolve the Intruder Alarm triggers from this step and step 2, untapping all creatures four times.
5. Activate Viscera Seer by sacrificing Belonging.
6. Activate Rat King by tapping it and sacrificing the Shapeshifters, returning Belonging from your graveyard to the battlefield.
7. Repeat from step 2.

This loop relies on Belonging to flood the board with changelings whenever it enters, which in turn triggers Intruder Alarm to keep untapping your entire team. Viscera Seer acts as the clean outlet to sacrifice Belonging to the graveyard, setting up Rat King, Verminister to tap and sacrifice those newly minted rats and shapeshifters to instantly return Belonging to the battlefield. Because Rat King, Verminister also triggers its own growth and token generation whenever permanents leave the battlefield, the whole engine feeds itself while generating an endless cycle of enters-the-battlefield, death, and untap triggers.