First Appearance: Book5 Prologue 14
Scottilus is an ancient Dread Naughtilus, a humongous aquatic nautilus-like creature possibly as old as Erfworld itself (remembers vaguely last 50,000 turns, but thinks he's much older than that). While he does not speaks language, he is sapient and capable of communicating via a special form of Signamancy that works via contact.
He was at one point tamed and still has a vehicle attached to him from that time (The Naughtilus Machine), but is currently fully feral and doesn't want to be tamed. If he was tamed, that side would have to pay a huge upkeep.
Scott travels by means of siphoning and spurting out great masses of seawater and can reach speed much higher than any sailing ships.
Given his age, and that he is the only known member of his kind, he may well have been created directly by the Titans.
Real World References
A dreadnought is a type of battleship, named after the iconic HMS Dreadnought which was launched in 1906. The signature characteristic of a dreadnought type battleship is that it has a uniform main battery in which all of the main guns are of the largest and most powerful type possible.
Dred Scott was an enslaved African American man in the United States who unsuccessfully sued for his freedom and that of his wife and their two daughters in the Dred Scott v. Sandford case of 1857, popularly known as the "Dred Scott case".