Prince of Pentos
The prince rides about the city in a palanquin of ivory and gold. Three heralds go before him carrying the golden scales of trade, the iron sword of war and the silver scourge of justice. On the first day of every New Year, the Prince must deflower the maid of the fields and the maid of the seas. However when the Pentoshi believe the gods are angry at them - such as after loss in a war or a crop failure - they sacrifice the prince by cutting his throat to appease the gods and then choose a new prince from amongst the forty families. 
It appears that the chosen prince has no say in whether he wants to be Prince of Pentos or not.
Over the course of the last two centuries, Braavos and Pentos fought no less than six wars. Four of them ended in Pentoshi submission. The last one, that ended a century ago, went so poorly that Pentos had no fewer than four princes chosen and sacrificed within a single year. The fifth one, Prince Nevio Narratys, convinced the magisters to sue for peace after a rare victory - one rumored to have been purchased by Nevio himself through bribery.
Years ago, an elected prince fled Pentos after being selected. When the Windblown’s Tattered Prince was twenty-three, the magisters of Pentos chose him to be their new prince almost right after they have beheaded the previous one. Instead of accepting their offer he fled to the Disputed Lands and never returned to Pentos.
Illyrio Mopatis grew so respectable that a cousin of the Prince of Pentos let him wed his maiden daughter. After Illyrio married his second wife, the palace gates were closed to him thereafter, but he did not care, the price was small enough, for Serra.
Past Princes of Pentos
- Nevio Narratys, who bribed the Braavosi to accept peace with Pentos after a victorious battle
- The Tattered Prince, who fled Pentos to avoid being made a sacrifice
- The cousin of Illyrio Mopatis' first wife.
Current Prince of Pentos
The identity of the current prince is not known.
– Tyrion Lannister, to Illyrio Mopatis