Overview
No one knows what the Starlight Roads were before the Collapse, but they undoubtedly hold magic of a power beyond imagining. Because of that - and because of the very nature of the Collapse - the danger within them is immense, for reality as it is experienced inside the Roads is warped by destabilised magic in ways without parallel anywhere else.
The sky within is forever full of stars, yet the Roads are always brightly lit, as though it were the middle of the day; the hour, however, is fixed at midnight, and there is no weather at all - no wind, no sense of temperature, no humidity. This does not hold inside structures or sealed containers, but as a rule it is so.
Time
Time and its effects lose all clear meaning within the Roads. According to Dykstra’s Continuum Theory, time is a constant that envelops every plane touching the Prime - which fits the observed fact that, no matter what is experienced inside, a traveller who enters the Roads and leaves again spends no more than a single day within them. What changes is perception, and the way time presses upon mind and body. In some regions time does not move at all: no hunger or fatigue ever comes, and spells and potions last for enormous stretches. In others a traveller will eat eight meals and sleep six times in a day, potions last only a moment, and spells vanish the instant they are cast.
Magic
Something in the strange space of the Roads makes magic behave badly. Beyond the distortions of time, there are regions where magic simply fails, regions where it works far more strongly than expected, regions where one spell triggers another, surprising one, and regions where a spell’s effects reverse or otherwise refuse to work as intended.
Navigation
Travelling the Roads is a peculiar art. Physical movement clearly matters - one cannot make progress without actually walking - yet intent matters just as much: one navigates by holding in mind the place one wishes to reach. Let the mind wander or lose its focus, and a traveller may find themselves somewhere else entirely. A traveller’s very thoughts hold some power over the world here; it is said that a single careless, mistaken thought once reshaped the ground itself. There seems to be a limit to how far thought can reshape the surroundings, but caution has never killed anyone.
Strange structures sometimes appear and vanish within the Roads, for reasons no one understands; at least one was found to hold traps and hostile things lying in wait for whoever entered.
Inhabitants
There are living things within the Roads, and they are seldom welcoming. Among them are beings that seem to belong properly to the Astral - including silver-sworded creatures of starlight whose presence in the Roads carries implications scholars are still untangling. There are also nilbogs and “sladabists” - held to be goblins and beasts that wandered into the Roads and stayed, utterly remade by the place - as well as mongrelfolk and a menagerie of other pseudo-creatures, all changed by their long dwelling here.
Researcher’s Notes
The scholar Kimyo counsels travellers to use as little magic as possible within the Roads. Cantrips are safe enough, but the stronger a spell, the likelier it is to trigger something powerful, and so its use should be weighed with care. From his study he observed certain tendencies: spells of evocation, illusion, abjuration and necromancy were the least likely to be disturbed by the place; divination sometimes returned false information and sometimes worked with greatly heightened effect; transmutation and conjuration were often affected; teleportation he had not yet tested, but suspected would suffer badly because of the spacetime distortions within; enchantment he had not tested at all. Magic items are affected only when their effects are active rather than passive - a wand, for instance - and when affected they behave much as spells do. Potions are not affected at all, and combined with the way their effects can linger for an extraordinarily long time, they are exceptionally useful in the Roads.
For travelling in company, his advice was that one person should always navigate, concentrating as hard as possible on the gateway to their goal, while the rest simply follow - keeping close, never letting too great a distance open up, and fixing their own concentration on following rather than merely walking alongside, lest their stray thoughts pull the navigation astray. Above all, avoid fights with the creatures wherever possible - not because they are necessarily so dangerous, but because every such battle risks dragging the party into the Roads’ unpredictable magic.
For the Dungeon Master
The shifting time and unstable magic of the Roads are resolved with dice tables - see Plane-The Starlight Roads Mechanics & Encounters.
Appendix
Sources & Attribution
Translated from the campaign’s original Hebrew notes on the Starlight Roads (the field research attributed in-world to Kimyo) and archived privately.