Chess was soon incorporated into the knightly style of life in Europe. Peter Alfonsi, in his work "Disciplina Clericalis," listed chess among the seven skills that a good knight must acquire. Chess also became a subject of art during this period, with caskets and pendants decorated in various chess forms. Queen Margaret of England had green and red chess sets made of jasper and crystal. Kings Henry I, Henry II and Richard I of England were chess patrons. King Alfonso X of Castile and Tsar Ivan IV of Russia gained a similar status.