The Viper

The Viper (died 1527) was the nickname given to a Templar located in Troyes, where the Templar Order was officially founded.

In 1527, Giovanni Borgia and Maria Amiel visited the city, with, unbeknownst to Maria, the goal of killing the Viper. The Viper was lured out by Maria and started talking to her, but was quickly stabbed from behind by Giovanni, thus killing him.

Source

 * Assassin's Creed: Project Legacy - Divine Science: Chapter 1 - Maria Amiel