Valkyrie's Call + Amoeboid Changeling + Spawning Pit + Flash Thompson, Spider-Fan

Valkyrie's Call

Amoeboid Changeling

Spawning Pit

Flash Thompson, Spider-Fan

How it works

1. Activate Amoeboid Changeling's second ability by tapping it, removing all creature types from Flash Thompson.
2. Activate Spawning Pit by sacrificing Flash Thompson.
3. When Flash Thompson dies, Valkyrie's Call triggers, returning Flash Thompson from your graveyard to the battlefield as an Angel with flying and a +1/+1 counter on it.
4. When Flash Thompson enters the battlefield, it triggers, untapping Amoeboid Changeling.
5. Resolve the Spawning Pit ability, putting a charge counter on it.
6. Repeat.

This looping engine relies on Amoeboid Changeling stripping away Flash Thompson, Spider-Fan's inherent creature types so it qualifies for Valkyrie's Call every single time it dies. By sacrificing Flash Thompson to Spawning Pit, you trigger Valkyrie's Call to instantly reanimate it, while the resulting entry trigger neatly untaps Amoeboid Changeling to keep the cycle going. Spawning Pit happily banks endless charge counters along the way, converting your infinite sacrifices into a massive swarm of Spawn tokens whenever you choose.