Stalwart Successor, Phyrexian Altar, and Gravelgill Axeshark

Prerequisites

• Stalwart Successor on the battlefield
• Phyrexian Altar on the battlefield
• Gravelgill Axeshark on the battlefield

Steps

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

Results

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