The River Ratterlin is the longest and most important river in the Old Kingdom. It stretches over 650 miles from its source in the Clayr's Glacier to its marshy delta on the east coast of the Kingdom, just south of Nestowe. The Ratterlin is the biggest source of running water able to keep the Dead away from it.
The Ratterlin begins in an underground spring deep below Starmount Mountain. As the river surfaces, it is fed by snow-melt from higher up the mountain and also small streams that traverse the Clayr’s Glacier. Here, close to its source, the river is about 45 metres (50 yards) wide and fairly shallow.
Progressing southwards down the Kingdom, the river greatly widens out to become half a mile wide and very deep, with clear, dark blue water. It is fed by two tributaries, the River Yanyl and one unnamed river. The Yanyl joins the Ratterlin just north of High Bridge. Approaching Abhorsen's House, the river speeds up and throws itself off the Long Cliffs in a waterfall, before sharply turning east and finally running on towards the sea.
As it runs the length of the Kingdom (from Clayr’s Glacier almost to the Wall), the Ratterlin is a useful method of travelling and transporting goods long distances. In Lirael, Sam says that usually many boats can be found along the river, even in winter.
Poem on the Ratterlin’s source
Recited by the Disreputable Dog in Lirael.
"Swift river born in deepest night,
Rushing forth to catch the light.
Deep ice and dark its swaddling cloth,
The Kingdom’s foes will feel its wroth.
Till mighty Ratterlin spends its strength,
In the Delta at full length."