During the quest "This Old Cove," you'll discover a mysterious gate inside the manor with the Templar Armor hidden behind it. This will trigger a new side quest focused on obtaining the keys needed to unlock the gate.
Edward finds the key for the locked away Templar Armor in the manor of Great Inagua.
To unlock the gate, you must acquire four keys held by four Templars: Hillary Flint, Jing Lang, Kenneth Abraham, and Lucia Márquez. To locate and eliminate them, you need to complete the questlines for four different Master Assassins.
Hillary Flint, Master Assassin: Rhona Dinsmore
Jing Lang, Master Assassin: Upton Travers
Kenneth Abraham, Master Assassin: Antó
Lucia Márquez, Master Assassin: Opía Apito
Once you have collected all the keys, simply return to the manor and open the door. Completing this quest rewards you with 10,000 Reales, 45 Bones, a new legendary outfit - Templar Armor, and a trinket - Templar Cross (Reduce damage from enemy melee attacks).
