The Abadon is an "Undead" monster. So it's very weak to "Holy", "Cure", etc types of magic. You will run into this beast on your way to Esthar to take Edea to Dr. Odine. This boss has two forms that it will use to counter its HP. In the first form, it's extremly weak to cure magic. In its second form, it stands up and uses more powerful attacks. Again, use cure magic. Your weapons won't do much damage to this beast. Afterwards when you have defeated in, you can proceed to Esthar.
