Phyrexian Altar + Dualcaster Mage + Persist

Phyrexian Altar

Dualcaster Mage

Persist

How it works

1. Cast Persist by paying its mana cost, targeting any applicable target.
2. Holding priority, cast Dualcaster Mage by paying its mana cost.
3. When Dualcaster Mage enters, it triggers, targeting Persist.
4. Holding priority, activate Phyrexian Altar by sacrificing Dualcaster Mage.
5. Resolve the Dualcaster Mage trigger, copying Persist, with the copy targeting Dualcaster Mage
6. Resolve the Persist copy, returning Dualcaster Mage from your graveyard to the battlefield.
7. Repeat from step 3.

This brilliant loop centers on Dualcaster Mage copying a spell mid-air, but it needs a clever engine to reset and sustain the magic. By casting Persist, you send a nonlegendary creature to the graveyard to be dragged right back with a -1/-1 counter, while Dualcaster Mage steps in upon entry to perpetually replicate that exact resurrection spell. Meanwhile, the humble sacrifice outlet Phyrexian Altar turns each iteration of this cycle into a fresh burst of any-color mana, fueling the loop infinitely while generating an endless stream of deaths and battlefield arrivals.