Cayth, Famed Mechanist, Mana Echoes, and Deceiver Exarch

Prerequisites

• Cayth, Famed Mechanist on the battlefield
• Mana Echoes on the battlefield
• Deceiver Exarch on the battlefield
• available

Steps

1. Activate Cayth by paying and tapping it, creating a copy of the Deceiver Exarch token
2. When the Deceiver Exarch token enters the battlefield, it and Mana Echoes trigger
3. Resolve the Deceiver Exarch trigger, untapping Cayth Resolve the Mana Echoes trigger, adding for each creature you control that shares a type with the Deceiver Exarch token
4. Repeat

Results

• Infinite ETB
• Infinite colorless mana
• Infinite creature tokens