Stalwart Successor + Phyrexian Altar + Safehold Elite

Stalwart Successor

Phyrexian Altar

Safehold Elite

How it works

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

This clever loop is fueled by Safehold Elite, which uses its persist ability to return to the battlefield with a -1/-1 counter whenever it dies. Fortunately, Stalwart Successor steps in right away to counteract that drawback, triggering the very first time counters are placed on a creature each turn to put a +1/+1 counter on Safehold Elite, which immediately annihilates the -1/+1 counter pair via state-based actions. With the Elite's slate wiped clean, you can freely feed it to Phyrexian Altar to generate an endless stream of colored mana alongside infinite sacrifice, death, and entry triggers.