The Princes of Florence: The Muse and the Princess (2009)

The Princes of Florence: The Muse and the Princess expansion adds 6 special character cards and a second auction phase.
From the rules:
"The expansion adds 6 special character cards which players can bid on in a second part of the auction phase. Thus, the auction phase has been split into two phases: the original auction phase and special character auction."

This expansion has not been released separately, but can be found in the Treasure Chest (only in Rio Grande version) and it is included in the recent versions of the game.

Contents:
6 special character cards
1 rule sheet