Stalwart Successor, Phyrexian Altar, and Persistent Constrictor

Prerequisites

• Stalwart Successor on the battlefield
• Phyrexian Altar on the battlefield
• Persistent Constrictor on the battlefield

Steps

1. Activate Phyrexian Altar by sacrificing Persistent Constrictor When Persistent Constrictor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
2. When Persistent Constrictor enters, Stalwart Successor triggers, putting a +1/+1 counter on Persistent Constrictor Repeat

Results

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