Sin, Unending Cataclysm + Intruder Alarm + Phyrexian Altar + Selvala, Heart of the Wilds

Sin, Unending Cataclysm

Intruder Alarm

Phyrexian Altar

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 triggers, untapping all creatures.
4. Activate Selvala by paying and tapping it, adding at least plus an additional X equal to Sin's power minus 3.
5. Activate Phyrexian Altar by sacrificing Sin, adding 1.
6. Choose to return Sin to the command zone from your graveyard.
7. When Sin dies, it triggers, putting its counters on Selvala.
8. Repeat.

This loop relies on casting Sin, Unending Cataclysm repeatedly from the command zone, transforming the massive influx of +1/+1 counters from its replacement effect into a permanent growth engine for Selvala, Heart of the Wilds. Each time Sin enters the battlefield, Intruder Alarm triggers to untap all creatures, allowing Selvala to tap for a staggering amount of mana fueled by Sin's ballooning power. You then sacrifice Sin to Phyrexian Altar to generate the exact mana needed to pay its commander tax and recast cost, while its death trigger moves all of those accumulated +1/+1 counters safely onto Selvala to make her tap for even more.