Jegantha, the Wellspring + Horde of Notions + Mass Hysteria + Yahenni, Undying Partisan

Jegantha, the Wellspring

Horde of Notions

Mass Hysteria

Yahenni, Undying Partisan

How it works

1. Activate Jegantha by tapping it, adding that cannot be spent to pay generic mana costs.
2. Activate Yahenni 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 puts Jegantha, the Wellspring's restrictive five-color mana ability to work by channeling its output directly into Horde of Notions, which uses those exact colored requirements to cast Jegantha straight back out of the graveyard for free. Mass Hysteria ensures that Jegantha's return to the battlefield is seamless, granting it immediate haste so it can tap again without waiting around. Meanwhile, Yahenni, Undying Partisan acts as the sacrificial engine that sends Jegantha back to the graveyard to feed the Horde, while safely harvesting endless death triggers and +1/+1 counters along the way.