Jegantha, the Wellspring + Horde of Notions + Tannuk, Steadfast Second + Phantom Train

Jegantha, the Wellspring

Horde of Notions

Tannuk, Steadfast Second

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 loop relies on Jegantha, the Wellspring generating the precise five-color mana required by Horde of Notions to repeatedly pull Jegantha straight back from the graveyard. To keep the cycle going, Phantom Train acts as the necessary sacrifice outlet, feeding on Jegantha while permanently growing larger with each iteration thanks to its own activated ability. Meanwhile, Tannuk, Steadfast Second ensures that Jegantha's re-entry is immediately ready for action by granting haste to your creatures, tying the entire mechanism together into an infinite engine for sacrifice and enters-the-battlefield triggers.