Jegantha, the Wellspring + Horde of Notions + Akroma's Memorial + Phantom Train

Jegantha, the Wellspring

Horde of Notions

Akroma's Memorial

Phantom Train

How it works

1. Activate Jegantha by tapping it, adding that cannot be spent to pay generic mana costs.
2. Activate Phantom Train by sacrificing Jegantha.
3. Activate Horde of Notions by paying , causing you to cast Jegantha from your graveyard without paying its mana cost.
4. Repeat.

This clever loop is fueled by Jegantha, the Wellspring, whose activated ability conveniently generates the exact five-color mana requirement needed to activate Horde of Notions. By using Phantom Train to sacrifice Jegantha, you bin the Elk Avatar so that Horde of Notions can immediately pull it right back out of the graveyard onto the battlefield without paying its mana cost. Because Jegantha's mana output perfectly matches Horde of Notions' activation cost, and Phantom Train happily turns each iteration into a +1/+1 counter for itself while feeding the sacrifice loop, the engine sustains itself indefinitely. Meanwhile, Akroma's Memorial stands ready to grant the entire board massive keyword buffs and protections to capitalize on the infinite sacrifices, enters-the-battlefield triggers, and storm count you've just unlocked.