Otherworldly Escort + Amoeboid Changeling + Thornbite Staff + Phyrexian Altar

Otherworldly Escort

Amoeboid Changeling

Thornbite Staff

Phyrexian Altar

How it works

1. Activate Amoeboid Changeling's second ability by tapping it, causing Otherworldly Escort to lose all creature types until end of turn.
2. Activate Phyrexian Altar by sacrificing Otherworldly Escort.
3. When Otherworldly Escort dies, it and Amoeboid Changeling trigger.
4. Resolve the Amoeboid Changeling trigger, untapping it.
5. Resolve the Otherworldly Escort trigger, returning itself from your graveyard to the battlefield as a Spirit Detective.
6. Repeat.