Magistrate's Scepter has at least one charge counter on it.
Six
Steps
1Activate Yawgmoth's second ability by paying and discarding a card, causing you to put a charge counter on Magistrate's Scepter.
2Ezuri triggers, causing you to draw a card.
3Repeat from step 1 two additional times.
4Activate 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.