Fossil Dragon is an undead enemy and the first enemy encountered that can inflict Zombie status. Locke can stealHoly Waters from them to recover the status. They can also use Sandstorm, which deals about two hundred damage to the entire party. The Fossil Dragon is weak to Holy-elemental attacks.
Sabin'sAura Cannon deals massive damage to it. Alternatively, the player can kill the Fossil Dragon by using a Phoenix Down or the aforementioned Holy Water on it, as it is an undead opponent. One can also simply confuse the dragon using Edgar'sNoiseblaster; even if one doesn't follow up with spells, it is possible that the Fossil Dragon will Banish itself out of existence.