Callixtus III

Pope Callixtus III or Callistus III (31 November 1378 – 6 August 1458), born Alfons de Borja, was Pope from 1455 to his death.

Callixtus was the uncle of Rodrigo Borgia, the eventual Grand Master of the Italian Rite of the Templar Order. In 2012, the Assassin Shaun Hastings took note of this, as his fellow Assassin Desmond Miles relived the memories of Ezio Auditore da Firenze, Rodrigo Borgia's arch enemy, through the Animus.

Reference

 * Assassin's Creed II