Mercurial Pretender, and Wispweaver Angel

Prerequisites

• Mercurial Pretender in hand
• Wispweaver Angel on the battlefield

Steps

1. Cast Mercurial Pretender by paying its mana cost, choosing to have it enter the battlefield as a copy of Wispweaver Angel When Mercurial Pretender enters the battlefield, it triggers, blinking Wispweaver Angel
2. When Wispweaver Angel enters the battlefield, it triggers, blinking Mercurial Pretender
3. Choose to have Mercurial Pretender enter the battlefield as a copy of Wispweaver Angel
4. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB