Jegantha, the Wellspring + Horde of Notions + Concordant Crossroads + Yahenni, Undying Partisan

Jegantha, the Wellspring

Horde of Notions

Concordant Crossroads

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 loop relies on Jegantha, the Wellspring generating the exact five-color mana required to fuel Horde of Notions's activated ability, which brings Jegantha right back from the graveyard for free whenever it hits the bin. To break the cycle, you sacrifice Jegantha to Yahenni, Undying Partisan, which not only sends the Elk Avatar back to the graveyard to be reanimated but also triggers Yahenni's growing +1/+1 counters and indestructible protection. Meanwhile, Concordant Crossroads ensures that Jegantha's return comes with immediate haste, allowing you to tap it for mana the very moment it hits the battlefield to keep the loop spinning endlessly.