Mikaeus, the Unhallowed + Phyrexian Altar + Safehold Elite

Mikaeus, the Unhallowed

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. Activate Phyrexian Altar by sacrificing Safehold Elite.
4. When Safehold Elite dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
5. Repeat.

This crafty engine hinges on a clever mathematical counter-cancellation trick powered by Mikaeus, the Unhallowed, whose static lord effect grants undying to your non-Human creatures like Safehold Elite. When you sacrifice Safehold Elite to Phyrexian Altar, its persist ability returns it with a -1/-1 counter, but sacrificing it *again* triggers undying instead, bringing it back with a +1/+1 counter that immediately annihilates the lingering -1/-1 counter through state-based actions. This infinite loop allows you to endlessly recycle Safehold Elite through Phyrexian Altar to churn out infinite colored mana and an endless cascade of death triggers.