Ouros

Ouros is the self-devouring serpent that surrounds Jurmangard. It is a monstrosity, easily a quarter-mile high, and constantly revolving because of the movement of his body. While moving, he is eating himself in a nasty, churning mess. Despite that, he's never any smaller.

Story Stuff
He gives Alcrisus the power to remove souls, in the hopes that he'll go crazy with it.

He is watching and manipulating several important characters throughout the series, including:
 * An evil Spirit Serpent+its cabal.
 * A Free Knights hold
 * An order of assassins?

He is the ultimate in-setting evil, and needs souls to power himself, to give energy. When Alcrisus is defeated, the souls will be returned, and he'll have to go dormant. This further means that people can escape, making the town of Bloodbay into the perfect jumping-off-point for exploration after the book is over, especially for characters like Vittore.

Symbolism
It's eating itself, thus showing destruction. However, despite the way that destruction and evil looks like it's gonna win, he never gains ground.

However, he can take away parts of himself temporarily, just as he's taking away the souls and memories of people.

Geographical Notes
Presumably, Ouros' self-eating shows as a bloodspill on one side of the map, all the way to shore at some town. Town is Bloodbay.

Since he is large and moving, he creates a tide, counter-clockwise (because evil things never go by the standard rules!), spiraling inward on the continent. This means that cliffs and such will have smooth clock-ward faces, with very rough splash zones behind them. It further means that there are a lot of jagged curves (sickle-like) pointed in a counter-clockwise direction.

Bays will likely have one solid side with sickle-curve (Ouros curve?), open inside.

Further, there are intense rip-tides, due to water coming in sideways, and then straight out.

He prevents anyone from escaping Jurmangard, but does create a nice trade current, allowing sea-serpent-towed ships to make amazing time around the borders of the continent. This, however, diminishes near land (farther from Ouros), meaning that the close to rivers parts aren't swamped. Rivers probably have larger than usual deltas though, due to current power.

Ouros' effect is not powerful enough to change rivers, but it does overcome moon forces, and is thus more tidal than Earth.