Reward: 800 Renown, 5000 Gold.
Go to the Hook Coast lighthouse and install the Heart on the strange panel at the top. Once you get down and talk to Briar, the artifact will be attacked by the Summoners. You have to defend it from them before they manage to destroy it. Summoners are tough opponents, they have lots of HP and are quite resistant to your blows. It's difficult to fight them using melee weapons only, but mixing it with Will powers gives satisfactory effects. Once you defeat them all, the Heart will summon a ship for you.