Dragon

Dragons exist in TwinWorld, and are continually fought by some of the Zarth. If you're talking about The Dragon that's a particular one.

Life and behaviour

Dragons come, with the air, from the depths of TwinWorld. They start as small worms, but as they drink the blood of living creatures they rapidly grow larger, disproportionate to their diet. They progress through looking something like snakes with barbs ridging their bodies, to a full grown dragon form, bristling with spines, claws, teeth, and clad in a double layer of impenetrable armor. They have no need to eat, but are motivated by their wicked desires to seek out new places to ruin. Many dwell under the earth, but some make their way into the upper airs, and prey on the Fayrie.

Metaphor

Dragons have heavy weight in story and metaphor. They are the symbol of evil, especially greed, lust, malice, and destruction. In the Scripture, dragons and Satan are synonymous. Satan is the prince of the power of the air, and so dragons are creatures of the air. Also, Satan can assume pleasing forms, and appear as an angel of light, so dragons too can shift forms. The dragon is seen emerging from a pit in Revelation, and so too the dragons come from the lowest depths of the earth.

Leviathan is (probably) another image of Satan, see Job 41 for a great description of a dragon.

In symbolizing greed, dragons hoard treasure, storing it uselessly and not even enjoying it themselves.

In symbolizing lust, dragons steal away and consume young women, or in this instance fay.

In symbolizing malice, dragons have cruel teeth, breath fire, and exude an aura of fear.

In symbolizing destruction, dragons tear down the works of others, and do not rebuild.