Gossamer

Gossamer is a dragon created by Dr. Harding, and was originally named the Centurion. It has blue scales and black spikes all over its body, as well as a series of massive wings which can be folded. Gossamer was first imagined in the Silo by Dr. Harding when he was young, and was created to protect children. Thus, Gossamer is naturally suspicious of all adults. Gossamer possesses the ability to breath fire, soft but strong scales, and a horn which it can use to impale food or enemies. Gossamer survived by eating the black, squid like creatures in the caves below Atherton, although it enjoys eating the black fig Isabel brings it. Apparently, Gossamer can fly through space without requiring any oxygen storing/producing equipment.

Gossamer in the series (Spoilers!)
Gossamer is discovered in Atherton: The Dark Planet by Isabel and Samuel. While searching for the Centurion and Edgar in the caves deep inside Atherton, they are chased by a gigantic monster. They are captured by Pythids, but freed by Gossamer, who spears the creatures with his horn and roasts them. He then proceeds to eat them, and shares them with the children. Isabel and Samuel realize that he is the Centurion and the monster than was chasing him. Isabel decides to rename him as Gossamer, on account of his soft wings. Using Black figs as lures, Isabel and Samuel succeed in guiding gossamer further, taking him to new regions. When they reach theGossamer waited in the Docking station with Isabel and Samuel, forcing them to stay until Edgar came back in the Raven by causing stalactites to collapse in front of the entrance of the cave. The children in the Silo love telling stories about Dr. Harding and Gossamer, who was portrayed as a protector of the young, to help distract themselves of the hardship of their life. When inside of Dr. Harding's study, they find several statues of Gossamer, which initially scares the children. When a hidden recording is activated, Dr. Harding states that Gossamer was unusually smart and intelligent, and "That's what you get when you start with a human brain, I suppose." When Edgar returned to Atherton, he brought along Red-eye and his brother. Gossamer roared loud enough to render them permanently deaf due to them being adults and being mean to the kids. Edgar had brought a block of powder in the Raven, which caused Gossamer to blow fire on the wall of white crystals, while the raven fired spikes into it. This led to the release of Winter, where thousands of white Ravens were activated and flew to earth to purify the air and ocean. Gossamer followed them to earth, and helped purify the planet by killing all the Spikers and Cleaners. Afterwards, he returns to the caves of Atherton.

Gossamer outside of the books
For many editions of the 3rd book in the series, Atherton: The Dark Planet, gossamer is featured on the cover.