The Isles: land, weather and seasons

How each world is raised from rock, rivers and climate; the seventeen kinds of wild country; the calendar and seasons; fifteen kinds of weather, snow that drifts and hail that falls as stones; light and dark; and the chart of your travels.

A world with bones

Every seed raises its own archipelago at true scale, about 1,050 km across, with the character of the British Isles but no real coastline. Each has its own main island (highest in the north, sometimes cut by a strait), peninsulas, one or two western islands, sea lochs and isles, on north-east to south-west structural spines with fractal coasts and a continental shelf.

Rock

The land begins as rock: fifteen geological provinces in Caledonian belts, among them basement gneiss, Highland schist, a rift valley, the Southern Uplands, Carboniferous limestone and gritstone, a slate massif, red-bed plains, Jurassic scarps, chalk downs, a granite peninsula, and an Irish plain and rim. Between them they hold 21 kinds of rock, cut by dykes and pierced by granite plutons, in dipping strata.

Rock is not just scenery. It decides what a pickaxe wins (copper in slate and schist, tin in granite, iron in red sandstone and the coal measures, lead in limestone: see Crafting), what building stone lies to hand, and which people build there.

Mountains and rivers

Uplift and the hardness of the rock drive a real erosion model, so hard rock stands as mountains and soft rock wears into vales. Rain falls on the western slopes from the westerlies and gathers into rivers that cut their own valleys, meander over floodplains, widen into estuaries and fill lakes. Navigable channels are at least six metres deep and deepen with their flow. Up close, each rock makes its own landforms: granite tors, limestone benches and pavements, basalt steps, gritstone edges, with soil over bedrock, bedding planes and flint bands.

Wild country

Temperature (from latitude and height) and rainfall choose seventeen biomes, each with its own soil and plants: machair, salt marsh, fen, meadow, chalk downland, beech hangers, oak-ash woods, Atlantic oakwood, Caledonian pine, heather moor, blanket bog, limestone pavement, montane heights and more. On the coasts grow kelp forests, eelgrass meadows and wrack; in lakes and rivers reeds, bulrushes, water-lilies and crowfoot.

Lordships and roads

The land is held in lordships of 20 km, each with a seat, its towns and hamlets, and roads between them, routed over the land at gentle grades, cut and embanked, and carried over rivers on stone arches or timber trestles. See Towns, trade and the watch.

The calendar

A world day lasts as many real minutes as you chose (24 by default), with the sun up for a share of it that lengthens in summer and shortens in winter. Each season lasts the days you chose (8 to 90; 24 by default), and four seasons make a year. Sowing, harvests, the weather, the leaves, beekeeping, the raiding season and everyone’s age follow the seasons.

The land changes with them: leaves turn and fall, grass tints and grows by the season, the snowline comes down the mountains and hoar frost lies in the morning.

Weather

Fifteen kinds of weather: clear, fair, cloudy, overcast, mist, fog, drizzle, rain, downpour, thunderstorm, hail, gale, sleet, snow and blizzard. A weather holds for a few hours and then gives way to the next, chosen by the season, the place (the wet western coasts rain far more than the dry east) and the temperature. Each blends in over an hour.

The weather drives:

the sky: cloud, sun, fog, and mist that pools in the valleys at dawn and under the canopy;
the wind: its strength and slowly veering direction (it fills sails and turns windmills);
what falls, around you and never under a roof;
wet ground that darkens and shines;
lying snow and lightning.

And play feels it: rain waters the fields, wind and wet chill the body, hail stings the bare-headed, and lightning finds the exposed on high ground.

Snow

Snow lies by height: deeper on the heights, where more of the year’s falls are snow and less of it melts, building in snowfall and melting in a thaw. Around you it is shaped by the land: snow carried on the wind drifts into the lee of ridges, banks, walls, hedges and houses and is scoured off the crests; steep ground sheds it; a crown of leaves catches much of a fall. Wading through deep snow leaves a trench (new snow fills it again) and slows you down.

Hail

Hail falls as real stones, each a body of ice of its own size, falling at the speed its size gives it, carried by the wind, slowed through leaves, ringing off stone and glass and dying in thatch and soil, rolling down roofs and slopes and lying until it melts. A big stone can chip glass, tiles, daub or shingles, and a long storm wears thatch and daub through. Pea hail does no harm; marbles sting; golf balls can kill. A helm keeps most of it off.

Light and dark

Light comes in physical proportion, from the 110,000 lux of a summer noon to the 0.3 lux of a full moon, and your eye adapts to it. On a moonless night out on the moor, firelight is precious: carry a torch, and remember that fires warm you as well. Light shafts cut through the trees, fireflies come out after sunset, and hearths smoke from town chimneys.

Growing woods

The woods grow over the world’s years at the pace chosen when the world was made. Trees move up through their sizes, age and die, and shoot again from a felled stool. Fellings and plantings are remembered with the world; seed gathered from standing trees in season can be sown in open soil.

The chart of your travels

Press M for your chart: a map of the world drawn from its own land (relief, woods, contours, rivers and lochs, settlements and roads, strongholds) as a surveyor’s inked and washed sheet. It shows only what you have walked or looked over; the rest is blank vellum. Your charts are kept with your character, one for each world. The chart’s Realms page draws the kingdoms over the sheet.

Written from the game's source and content as of commit 02e81b2 (2026-11-01).