Green dragons are most notable for the large, waving crest or fin that starts at the dragon's nose and runs the entire length of the dragon's body. They also have exceptionally long, slender forked tongues. Green dragons expel a cone of corrosive chlorine gas. 
They are mean-tempered, cruel, and rude. These dragons love intrigue and secrets. They delight in stalking their enemies and listening in for any information they can gather before moving to attack. Green dragons enjoy consuming elves and fey creatures, especially pixies.
They are highly territorial, and will often view any intrusion into their domain, voluntary or not, as a personal affront. They are extremely cunning and duplicitous foes, and love double-crossing others. A traveler who stumbles into a green dragon's territory may be able to bribe the dragon for safe passage, but more often than not the dragon will pretend to agree and then attack the unsuspecting offender once their guard is down. 
Green dragons dwell in deep, old-growth forests. The typical green dragon lair will be a complex of caves and tunnels, with its main entrance hidden behind a waterfall. The preferred green dragon lair is a cave high up on a cliff, but such locations are usually hard to find and thus only home to the oldest and most powerful green dragons.