Sin, Unending Cataclysm + Intruder Alarm + Blasting Station + Selvala, Heart of the Wilds

Sin, Unending Cataclysm

Intruder Alarm

Blasting Station

Selvala, Heart of the Wilds

How it works

1. Cast Sin either from your hand or command zone by paying 5 plus commander tax if applicable.
2. As Sin enters, remove all counters from all artifacts, enchantments and creatures you control, putting twice that many +1/+1 counters on Sin.
3. When Sin enters, Intruder Alarm and Blasting Station trigger, untapping all creatures and Blasting Station.
4. Activate Selvala by paying and tapping it, adding at least plus an additional X equal to Sin's power minus 3.
5. Activate Blasting Station by tapping it and sacrificing Sin.
6. Choose to return Sin to the command zone from your graveyard.
7. When Sin dies, it triggers, putting its counters on Selvala.
8. Resolve the Blasting Station ability.
9. Repeat.

This loop turns Sin, Unending Cataclysm into an endlessly recurring threat by abusing the continuous enters-the-battlefield triggers provided by Intruder Alarm and Blasting Station. As Sin enters the battlefield, its replacement effect strips counters from your permanents to grow huge, which in turn supercharges Selvala, Heart of the Wilds's tap ability to generate massive amounts of colored mana while feeding card draw. You then sacrifice Sin to Blasting Station to deal damage and send it back to the command zone, while Intruder Alarm's static untap ability instantly readies both Selvala and Blasting Station for the next iteration.