Missy, Phyrexian Altar, and Horde Ambusher

Prerequisites

• Missy on the battlefield
• Phyrexian Altar on the battlefield
• Horde Ambusher on the battlefield
• You have at least one red card in hand

Steps

1. Activate Phyrexian Altar by sacrificing Horde Ambusher, adding one mana of any color
2. When Horde Ambusher dies, Missy's first ability triggers, returning Horde Ambusher from your graveyard to the battlefield face down as a 2/2 Cyberman artifact creature
3. Activate Horde Ambusher's morph ability by revealing a red card from your hand, turning it face up
4. Repeat

Results

• Infinite colored mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers