Wooden Shield - Available free at the Docks/Harbor.
Unbreakable | +2 Defense

Bronze Shield - Inside Haven Accessory Shop for 1,500 Gold. Haven Sentinels drop them also which are located all over Haven town.
Unbreakable | +10 Defense

Mithril Shield - 75 Corrupted Necklaces(s) and 50 Essences of Corruption The necklaces are dropped by Corrupted Fairies and the essences are dropped by Corrupted Sprites Unbreakable | +30 Defense

Ring of Protection - 125 Lizard Shield(s), 50 Spark Crystal(s), 100 Toad Axe(s) which is dropped by items in Khatru, Lizard Shields are dropped by Lizardman, Spark Crystals are dropped by Enigmas, and Toad Axe(s) are Giant Toads. Trade in the Lizard Shields and Spark Crystals for a Flawed Gem of Protection, then the Flawed Gem of protection and Toad Axes for Ring of Protection
Unbreakable | +55 Defense

Shield of Valour - 50 Frozen Orbs and 300 Snowflakes. Frozen Sprites Drop 1 Frozen orb 1/10 and Ice demonesses drop 1 snowflakes 1/2. Frozen sprites are above Subzero town and Snowflakes are in the falls below Subzero town.

Unbreakable | +70 Defense

Aegis Shield - Goregof Hide, 1,200 Shield Fragments, 300 Mauler Pelts required. An NPC called Goregof drops a Goregof Pelt, who is located inside a cave on the way to Sub Zero town. You then need to go and collect 1200 Shield Fragments, which are dropped by Alkanor Spear-Knights, located at Alkanor, near the yellow gate inside the house. Then you need 450 Mauler Pelts, which are dropped by Maulers, located on the Hidden Island. There is also one Mauler in a white zone, on the way to Kenshi town, there is a small cave where you can kill the Mauler safely. Once you have the materials, go inside one of the Western houses in Alkanor for the final trade in. Congratulations.
Unbreakable | +150 Defense