Eternity Vessel + Magistrate's Scepter + Donatello, Mutant Mechanic

Eternity Vessel

Magistrate's Scepter

Donatello, Mutant Mechanic

How it works

1. Cast Eternity Vessel by paying 6. It will enter with a number of charge counters on it equal to your life total.
2. Cause Eternity Vessel to leave the battlefield. When it does, Donatello triggers, putting a number of charge counters on Magistrate's Scepter equal to the number Eternity Vessel had on it.
3. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.
4. Repeat step 3 as able each turn.