Activate Pentavus to create a Pentavite by tapping a mana rock which produces at least 2 mana. Then use the second mana and sac the Pentavite to activate the Pentavus again. The dying Pentavite triggers the Dross Scorpion allowing you to untap the mana rock. This produces infinite ETB triggers, death triggers, and mana (if the rock produces more than 2).