In Assassin's Creed II, Leonardo da Vinci helps Ezio Auditore decode Altaïr's Codex pages. Leonardo is one of Ezio's most important allies and applies his artistic and engineering talents to the mysterious documents.
Ezio meets Leonardo in Florence, where Leonardo's workshop becomes a recurring place for story development and equipment improvements. He translates the Codex pages, which contain historical information, maps, and technical designs connected to the Assassin Brotherhood.
The game uses Leonardo's real reputation as a painter, inventor, and engineer, but places him inside a fictional conspiracy involving the Templars and the Apple of Eden. Several inventions associated with Leonardo are also adapted for gameplay, including a flying machine used during Ezio's missions.
A common mix-up is naming another famous Renaissance artist. Michelangelo and Raphael were real contemporaries, but Leonardo is the character directly linked to Ezio's Codex translations and inventions.