Which historical inventor helps Ezio build inventions in Assassin's Creed II?

Leonardo da Vinci helps Ezio build inventions in Assassin's Creed II. In the game, Leonardo is a close ally who applies his engineering and artistic skills to support Ezio's missions.

Leonardo deciphers pages from Altaïr's Codex, a collection of Assassin knowledge, and uses the information to create or improve equipment. His contributions include upgraded hidden blades, a poison blade, a flying machine, and other devices used during the story. The game places these fictional inventions within Leonardo's real Renaissance career.

The historical Leonardo was born in 1452 and became one of the most famous artists, scientists, and engineers of the Renaissance. He worked in Florence, Milan, and elsewhere, and his surviving notebooks contain studies of anatomy, mechanics, flight, and architecture.

Assassin's Creed II does not claim that every invention shown was genuinely built by Leonardo. The series deliberately mixes documented history with speculative technology and fictional conspiracies. Leonardo returns as an important ally in Assassin's Creed Brotherhood, which continues Ezio's story in Rome.