Kenrith, the Returned King + Smothering Tithe + Xorn + Bard, King of Dale

Kenrith, the Returned King

Smothering Tithe

Xorn

Bard, King of Dale

How it works

1. Activate Kenrith's fourth ability by paying 3, causing an opponent who cannot pay for Smothering Tithe's trigger to draw a card.
2. Smothering Tithe triggers, causing you to create four Treasure tokens due to Xorn and Bard.
3. Activate the Treasures by tapping and sacrificing them, adding 3.
4. Repeat.

This loop thrives on an explosive multiplication of resources, turning Kenrith, the Returned King's blue activation into a self-sustaining engine. When Kenrith forces an opponent to draw, Smothering Tithe triggers if they fail to pay the tax, attempting to create a Treasure token. Because Xorn and Bard, King of Dale both feature replacement effects that double token creation, that single Treasure is amplified into four. Sacrificing just three of those Treasures easily pays the {3}{U} needed to activate Kenrith again, leaving you with a growing surplus of mana and infinite draws for your opponents.