Sakashima of a Thousand Faces + Felidar Guardian

Steps

1. Cast Sakashima of a Thousand Faces either from your hand or from the command zone by paying {3}{U} plus commander tax, if applicable, choosing to have it enter the battlefield as a copy of Felidar Guardian
2. When Sakashima of a Thousand Faces enters the battlefield, it triggers, blinking Felidar Guardian.
3. When Felidar Guardian enters the battlefield, it triggers, blinking Sakashima of a Thousand Faces. Choose to have Sakashima of a Thousand Faces enter the battlefield as a copy of Felidar Guardian.
4. Repeat from step 2.