There are nine isotopes of elemental fire which can be found in nature, though only five of these are stable. Classical fire, the sort which lights candles and powers engines, consists on the atomic level of exactly eight protons, eight neutrons, and eight electrons. For this reason, it is often mistaken for oxygen during experiments in modern chemistry. Remove one neutron from this arrangement, and the resultant isotope is phlogiston, classical fire’s nearly indistinguishable cousin. Remove yet another neutron, however, and the result is a volatile substance known to natural philosophers as phlox borealis.

The natives of Hyperborea have another name for it: “magnetic fire.”

In times before recorded history, phlox borealis was used as a weapon of war, and was as reliable as any compass; when fields or prairies were set alight with its violet flame, it always spread due north, regardless of what it found along its path. Invading armies would arrange their phalanxes along a city’s southern border, then pour jars of the hissing substance onto the earth at their feet. This fearsome tactic left stripes across the world’s skin. The inferno would crawl over stone walls, through metal pipes, and even across sheets of solid ice to maintain its momentum, only ever stopping if it arrived at a body of water.

Some of these burning paths never met such an end, however, and made it all the way to Hyperborea- a land further north than even the planet’s northernmost pole. Here, beyond the borders of the mappable world, its restless tongues finally began to slow down, for there was nowhere further north to wander. Without any fuel to sustain its energy, the magnetic fire cooled until no longer dangerous to the touch, then pooled in wounds in the landscape left behind by glaciers.

Today, only rivers and lakes remain where this phenomenon once took place. This is because, like all other unstable isotopes in nature, magnetic fire eventually undergoes decay. When it happens, two protons and two electrons are ejected from the nucleus as hydrogen atoms, leaving carbon behind. These two strays then bind with nearby classical fire ions, the result of which is a molecule recognizable to any modern chemist: liquid water.