Sin, Unending Cataclysm + Intruder Alarm + Ashnod's Altar + Heronblade Elite

Sin, Unending Cataclysm

Intruder Alarm

Ashnod's Altar

Heronblade Elite

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 Ashnod's Altar by sacrificing Sin, adding CC.
5. Choose to return Sin to the command zone from your graveyard.
6. When Sin dies, it triggers, putting its counters on Heronblade Elite.
7. Activate Heronblade Elite by tapping it, adding an amount of or equal to its power.
8. Repeat.

This loop transforms the recursive entry of Sin, Unending Cataclysm into an engine of endless power and mana. Every time Sin enters the battlefield, Intruder Alarm triggers to untap all your creatures—including Heronblade Elite, which is growing rapidly thanks to the massive pile of +1/+1 counters Sin dumps onto it upon dying. You then sacrifice Sin to Ashnod's Altar for colorless mana, choose to return Sin to the command zone so you can recast it, and tap the supercharged Heronblade Elite to flood your pool with colored mana.