The ordinary properties of rivers (especially named rivers), whether as territorial boundaries, defensive lines or trade/transport routes, tend to be echoed on a deeper level in fantasy. Here the boundary may be between Good and Evil; the defence may be against Thinning or incursion by a Dark Lord – Anduin, the Great River, is a significant line of defence in J R R Tolkien's The Lord of the Rings (1954-1955) – or by Witches, who traditionally cannot cross running water except in a boat made of eggshell. Rivers may be barometers of the Land through which they flow, a diseased river indicating a general need for Healing. Their age and continuity of flow indicate the ancient nature of the land's Story (see also Time Abyss). Subterranean rivers like Alph in Xanadu (see also Samuel Taylor Coleridge) have a special resonance, as does the Thames in London and the Rhine in Richard Wagner's Ring cycle.
The liquid in a fantasy river may have any property of a Potion. Notoriously, the river Lethe brings Amnesia, and the name of the Fountain of Youth is self-explanatory. An oddity of magical ecology in Piers Anthony's A Spell for Chameleon (1977) is a barren river wishing to restock itself: drinking its water brings Transformation into a fish. What flows in some rivers may be not water but Stars, souls, the stuff of Magic, or – as with Hell's river Phlegethon – boiling blood. Rivers may contain tutelary Gods, as encountered in C S Lewis's Prince Caspian (1951) and Gene Wolfe's Solder of the Mist (1986); other denizens may include Dragons, Selkies, and nymphs or naiads who may or may not be perilous, like the Lorelei (see Mermaids; Sirens). Travelling along or across any important river may mean a change of condition more significant than movement on the Map: by crossing a mere brook, Alice in Lewis Carroll's Through the Looking-Glass (1871) becomes a queen. [CB/DRL]