Lazav, the Multifarious + Putrid Goblin + Ashnod's Altar + Strangleroot Geist

Lazav, the Multifarious

Putrid Goblin

Ashnod's Altar

Strangleroot Geist

How it works

1. Activate Lazav by paying 2, choosing to have it become a copy of Putrid Goblin if it doesn't have a -1/-1 counter on it, or Strangleroot Geist otherwise.
2. Activate Ashnod's Altar by sacrificing Lazav, adding CC.
3. When Lazav dies, if it was a copy of Putrid Goblin, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
4. Otherwise, Lazav's undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
5. When Lazav enters the battlefield, it triggers, causing you to surveil 1.
6. Repeat.

This ingenious loop revolves around Lazav, the Multifarious dynamically adapting its identity to fuel an infinite engine with Ashnod's Altar. By paying {2} to transform Lazav into a copy of Putrid Goblin, you can sacrifice it to the altar for two mana and let persist bring it back with a -1/-1 counter. Because a +1/+1 counter and a -1/-1 counter annihilate each other as a state-based action, you can then pay {2} to turn Lazav into a copy of Strangleroot Geist, sacrifice it again, and let undying return it with a +1/+1 counter to reset the cycle. Every iteration of this shapeshifting dance triggers Lazav's surveil 1 ability upon entering the battlefield, letting you effortlessly churn through your deck while generating infinite sacrifices.