Otherworldly Escort + Amoeboid Changeling + Intruder Alarm + Ashnod's Altar

Otherworldly Escort

Amoeboid Changeling

Intruder Alarm

Ashnod's 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 Ashnod's Altar by sacrificing Otherworldly Escort.
3. When Otherworldly Escort dies, it triggers, returning itself from your graveyard to the battlefield as a Spirit Detective.
4. When Otherworldly Escort enters, Intruder Alarm triggers, untapping all creatures.
5. Repeat.

This clever loop turns Otherworldly Escort into an immortal sacrifice engine by exploiting its own resurrection clause. Because Otherworldly Escort returns to the battlefield only "if it's not a Spirit" when it dies, Amoeboid Changeling's ability is used to strip away its creature types just before Ashnod's Altar converts it into a pair of colorless mana. Every time Otherworldly Escort successfully loops back onto the battlefield, Intruder Alarm untaps all your creatures—including Amoeboid Changeling and Ashnod's Altar—allowing you to repeat the cycle indefinitely for infinite mana and triggers.