The Defender's Shield is a very well-balanced medium shield with 100% physical damage reduction, strong elemental defenses and good status effect resistances. It is most notable for having very good stability, tied for the highest base stability alongside the Old Knight's Shield, while being significantly lighter and much more durable. It is slightly heavier than the average medium shield, but it is still manageable and well worth the weight, given its strengths.
However, obtaining the Defender's Shield requires defeating the Throne Watcher and Defender, which are end-game bosses that can only be accessed after obtaining the King's Ring. Additionally, upgrading the Defender's Shield requires Petrified Dragon Bones, which can potentially be difficult to come by.