Around 1506, Demetrio was forced by Cesare Borgia to copy blueprints for the Hidden Blade stolen from Monteriggioni and to modify a Hidden Blade stolen by the Templars to create an upgraded version of it, called "the Corvix Blade".
When Demetrio refused to continue creating more weapons for him, Cesare cut his tongue. This caused Demetrio to plot against Cesare, asking the Assassins for help. Anyway, Cesare found out about his plan and arranged his execution. However, right before he could be executed, Demetrio was saved by an Assassin and then taken into custody by Machiavelli. There, Demetrio revealed the existance of the Corvix Blades to the Assassins.