Cayth, Famed Mechanist, Mana Echoes, and Hyrax Tower Scout

Prerequisites

• Cayth, Famed Mechanist on the battlefield
• Mana Echoes on the battlefield
• Hyrax Tower Scout on the battlefield
• available

Steps

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

Results

• Infinite ETB
• Infinite colorless mana
• Infinite creature tokens