Sin, Unending Cataclysm + Intruder Alarm + Phyrexian Altar + Heronblade Elite

Sin, Unending Cataclysm

Intruder Alarm

Phyrexian 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 Phyrexian Altar by sacrificing Sin, adding G/U.
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 clever loop turns Sin, Unending Cataclysm into an infinitely recastable engine by leveraging its unique replacement effect to strip its own counters, allowing it to die repeatedly to Phyrexian Altar while feeding its accumulated power back into Heronblade Elite. Each time you cast and sacrifice Sin, Intruder Alarm untaps your board, letting Heronblade Elite tap for massive amounts of mana proportional to the immense stack of +1/+1 counters Sin leaves behind upon dying. Because Sin shuffles itself away or can be redirected to the command zone to reset its mana cost, you can endlessly replay it to fuel infinite enters-the-battlefield triggers, death triggers, and colored mana.