Felidar Guardian + Machine God's Effigy

Steps

1. Cast Machine God's Effigy by paying {4}.
2. Choose to have Machine God's Effigy enter the battlefield as a copy of Felidar Guardian, except it's an artifact.
3. When Machine God's Effigy enters the battlefield, it triggers, blinking Felidar Guardian.
4. When Felidar Guardian enters the battlefield, it triggers.
5. Holding priority, activate Machine God's Effigy by tapping it, adding {U}.
6. Resolve the Felidar Guardian trigger, blinking Machine God's Effigy.
7. Repeat from step 2.