lore stuff

The lore is that carbuncles are lesser dragons; the power lays within them but cannot be awoken without external interference.

They are earth-aspected creatures - each mined gemstone in a magic-rich area can become a new carbuncle. Gemstones being their source of life, they congregate at mines where new Steorlings may be born. This mining also generates metal ores and an abundance of silver, which they've adapted for use as their main currency/trading resource. It's important to note that this is more or less sustainable in this world, as gemstone minerals form as a crystallisation of magic in the earth; it can be seeded and grown predictably, akin to growing crops year-round, though on a slower scale. (An area will be mined out, then seeded as another area is mined out in rotation)

The underground is a vast cave system, consisting of massive caverns with glittering ceilings, underground seas, deep ravines...etc. There are light sources for the underground too. Tunnels have been made connecting some nearby large settlements, which are safer to use than the aboveground routes, but sometimes this isn't possible to do.

The infection corrupts the earth such that the natural magic drains away and gemstones turn to dust in the ground. While the underground has been largely safeguarded from this effect by virtue of being far underground (which initially caused the Steorlings to flee underground and create their subsurface settlements), the spreading of the infection means that it's only a matter of time before it hits the mines. When a wish is made upon a star, an area of earth may be protected from this effect by the star for as long as that Steorling is alive, and multiple wishes to cover large areas have been how some of the oldest mines and travel routes have been preserved. With this as a weapon against the infection, current sentiment among Steorling leaders is that they should take back territory on the surface. Hence the establishment of new surface towns is being funded, and Crossers primarily dwell on the surface (there's hardly any need for them to be underground).