Attacking his head will cause very little damage, but it is the simplest way to beat him. Performing a paraloop as close to the tip of his tail as possible will kill him instantly. This is the only boss to have an instant-kill move.
A translated Japanese bio for Gillwing states:
"By Second Level standards, he’s got a huge, enormous body but he’s really just a big air-head. The moment he considers you an enemy, he’ll stop at nothing to chase you down. He possesses the ability to re-grow his head from his long tail."
- The star at the top of the Nightmaren tree-like formation in Gillwing's realm in NiGHTS into Dreams actually has use in Christmas NiGHTS into Dreams as after you defeat the "Christmas Gillwing" you are awarded the star that will eventually sit atop a very tree-trimmed Twin Seeds tower. This will win you the game in Christmas NiGHTS, but you do not recieve the star at the end of the battle in the original game.
- Gillwing's theme is called "The dragon gave a loud scream".
- Gillwing appears in the Nightmare Zone DLC for Sonic Lost World, as the Nightmaren that Zavok is riding on.