Viggo's Titan Wing Shellfire's existence is first implied in "Twintuition", in which Viggo refers to a "Project Shellfire"; the silhouette of the dragon itself later appears at the end of the episode supporting a vessel made from dragon-proof metal.
Ryker subsequently takes the Shellfire and the Dragon Hunter Ships to Dragon's Edge, and due to the Shellfire's attack range is able to assault the riders from a safe distance while preventing them from counterattacking. Viggo is able to counter this by disturbing a Submaripper, the Shellfire's natural enemy, which attacks the Shellfire. This distraction allows the Dragon Riders to attack and free the Shellfire from Ryker's control.
As its name implies Viggo's Titan Wing Shellfire is a Titan Wing Shellfire, and is thus larger, more brightly colored, stronger, heavier, and has more pronounced features than a Broad Wing Shellfire. Probably a male individual, Viggo's Shellfire sports a dark magenta/light maroon-colored body, most notably: face, head, nasal horn, underbelly, limbs and pupils. It has golden-yellow dorsal shell, tail spikes and cranial horns, along with amber-colored spots along its back. Viggo's Shellfire's teeth are irregularly arranged in the dragon's mouth, and it is missing the tip of its right cranial horn.
The Dragon Hunters planned for Viggo's Shellfire to service them as their ultimate weapon in their war against the Dragon Riders, 'Project Shellfire', and captured and held it captive against its will for what was probably weeks, adding a massive dragon-proof vessel on its back and forcing the timid dragon to attack various islands of the archipelago and battle a Submaripper, much to the Shellfire's dismay. Upon release the enslaved dragon immediately dove into the ocean, finally free of its metal bonds.
It is unknown what kind of relationship Viggo's Shellfire has with Viggo, as they have never been seen together or seen interact in any significant way, mostly due to Viggo seeing his Shellfire as a super weapon and means-to-an-end instead of a dragon, much like Drago Bludvist with his Bewilderbeast. Also, Viggo's possession of the Shellfire was cut short due to Ryker's betrayal and eventual release of the Shellfire.
Just like his brother Viggo, Ryker saw the Shellfire as means of defeating his brother and the Dragon Riders and terrorizing the Archipelago, and had a slave driver-slave relationship with the dragon. Ryker ordered his men to control and torture the Shellfire to do his bidding and got irritated when the Shellfire hesitated at terminating the fallen Dragon Riders as well as when the Submaripper arrived to challenge the dragon, and urged it to defend itself from the Submaripper's and the Rider's attacks.
Not much interaction was shown between the Dragon Riders and Viggo's Shellfire, other than that the Rider's were surprised upon its discovery and dismayed at it being enslaved by the Hunters, and did their best to try to stop Ryker while trying to avoid harming the dragon. Viggo's Shellfire seemed reluctant to fire at the downed Dragon Riders while Ryker ordered it to do so, meaning the dragon wasn't successfully enslaved and didn't want to harm others.
Being the natural enemy of the Submaripper, Viggo's Shellfire seemed distressed at the sudden appearance of Shipsbane, and both dragons proceeded to immediately start brawling each other, with the more agressive Submaripper taking on the offense and the Shellfire defense. The battle ended in a tie when Shipsbane broke the Shellfire's bonds allowing it to escape into the depths of the sea.
This individual is the only known member of its species.
It is also the only known Titan Wing member of its species.
It remains unknown as to what is meant with the Titan Wing title in this dragon, since it is used as both the final stage in any dragon's life and to describe large species or subspecies of dragons, notably the Screaming Death.