Aaron was the first abbot of Benedictines, who were brought to Krakow by Casimir I the Restorer. According to some records Aaron was born in the Cologne. He became the fifth bishop of Krakow in 1045, after Czech prince Bretislav destroyed Gniezno in 1048 he became the archbishop of Poland. The legend says he was also the first abbot of Benedictine monastery in Tyniec, but according to the documents the monastery was founded only in 1075. Aaron died in 1059 and was buried in Wawel Cathedral.
Aaron’s shield looks like three golden crowns on the silver field. It is used as the official shield of Krakow chapter till today. You can see it on some buildings in Krakow Old Town owned by Krakow chapter. The other theory says that this shield was modelled on the shield of Cologne chapter, as according to the legend Three Kings were buried in the Cologne Cathedral.