Duke Horacio

Duke Horacio is the duke of Lumbridge and the surrounding area. He lives on the of the Lumbridge Castle in a room with a quest marker in it. He also hands out anti-dragon shields to players during the Dragon Slayer quest. More shields can be obtained via the drop trick.

Another way to obtain the shield is to buy from it Oziach for 26 coins, who has a total stock of 35.

Trivia

 * In RuneScape Classic, he was simply known as Duke of Lumbridge.