Templar key
The Templar keys were a set of fives keys which together granted access to a vault in the manor on Great Inagua. The keys were entrusted to five Templars station in the Caribbean: Julien du Casse, Hilary Flint, Lucia Márquez, Kenneth Abraham, and Jing Lang. After the pirate Edward Kenway delivered a map showing the locations of Caribbean Assassin bureaus to the Templars, the keyholders excluding Du Casse were each assigned a bureau leader to execute.
When Edward assassinated Du Casse and procured the first key, he discovered the vault it unlocked contained a desirable set of armor. Upon discovering a map showing the locations and missions of the keyholders, he agreed on Mary Read's insistence to warn the targeted Assassins, provided it led him to the other four keys.