Altered Ego + Felidar Guardian

Prerequisites

You have enough mana to cast Altered Ego.

Steps

1. Cast Altered Ego by paying its mana cost, choosing to have it enter the battlefield as a copy of Felidar Guardian
2. When Altered Ego enters the battlefield, it triggers, blinking Felidar Guardian.
3. When Felidar Guardian enters the battlefield, it triggers, blinking Altered Ego. Choose to have Altered Ego enter the battlefield as a copy of Felidar Guardian.
4. Repeat from step 2.