Commander Liara Portyr + Appa, Steadfast Guardian + Felidar Guardian

Commander Liara Portyr

Appa, Steadfast Guardian

Felidar Guardian

How it works

1. Declare two creatures as attackers, ensuring to attack two different opponents. Commander Liara Portyr triggers, causing spells you cast from exile this turn to cost 2 less to cast.
2. Cast Appa by paying its mana cost.
3. When Appa enters, it triggers, exiling Felidar Guardian with the ability to cast it from exile later.
4. Cast Felidar Guardian from exile by paying 0 due to Commander Liara Portyr.
5. When Felidar Guardian enters, it triggers, blinking Appa
6. Repeat from step 3.

This brilliant loop centers on Commander Liara Portyr, whose attack trigger makes spells cast from exile cost {2} less when you swing at two opponents, setting the stage to cast Appa, Steadfast Guardian with a deep discount. When Appa enters the battlefield, its airbend ability exiles Felidar Guardian, and because Liara Portyr's cost reduction lowers Felidar Guardian's exile-casting cost to zero, you can play it entirely for free. That free casting triggers Appa, Steadfast Guardian's second ability to churn out a 1/1 white Ally creature token every single iteration. Finally, Felidar Guardian's own entrance triggers a blink on Appa, Steadfast Guardian so it re-enters the battlefield to airbend Felidar Guardian all over again, keeping this engine of infinite value humming indefinitely.