Sicco

Sicco, also spelled Sikko or Siggo, was a Prussian pagan priest of the Prussian ethnic religion active in the second half of the tenth century, and the leader of the group responsible for the killing of Adalbert of Prague. He is known only through the two earliest hagiographic works dedicated to the martyr, and the name by which he is known is generally considered a conventional name rather than a historically verified one.