Bladewing the Risen + Dack's Duplicate

Prerequisites

You have enough mana to cast Dack's Duplicate

Steps

1. Cast Dack's Duplicate by paying its mana cost, choosing to have it enter the battlefield as a copy of Bladewing.
2. Put Bladewing into your graveyard due to the legend rule.
3. Dack's Duplicate's enter-the-battlefield ability triggers, returning Bladewing from your graveyard to the battlefield.
4. Put Bladewing into your graveyard due to the legend rule.
5. Bladewing's enter-the-battlefield ability triggers, returning it from your graveyard to the battlefield.
6. Repeat from step 4.