Lathliss, Dragon Queen, Bladewing's Thrall, Leyline of Transformation, and Yahenni, Undying Partisan

Prerequisites

• Lathliss, Dragon Queen on the battlefield
• Bladewing's Thrall in hand
• Leyline of Transformation on the battlefield
• Yahenni, Undying Partisan on the battlefield
• Leyline of Transformation on the battlefield with "Dragon" chosen
• available

Steps

1. Cast Bladewing's Thrall by paying
2. When Bladewing's Thrall enters the battlefield, Lathliss triggers
3. Holding priority, activate Yahenni by sacrificing Bladewing's Thrall
4. Resolve the Lathliss trigger, creating a 5/5 Dragon creature token
5. When the Dragon enters the battlefield, Bladewing's Thrall triggers, returning itself from your graveyard to the battlefield
6. Repeat from step 2

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite creature tokens