From the introduction:
Life is brutally pseudomedieval. The serfs work the land until they collapse in the dust, the nobles rule their subjects with an iron hand. Towns are small and few, with a few simple craftsmen plying obvious dark-age-level technical trades. The Church keeps a tight reign on knowledge, especially magic. No one's ever seen an elf or a magic sword, although people believe in them.
But hidden from the mainstream is a whole underworld of illegal sorcerers practicing the Forbidden Arts, communicating via an astral void scattered with islands of pseudoreality. Pure sorcerers forget the gritty reality entirely and focus on exploring or constructing astral isles; others sell themselves as assaultmages to politically ambitions nonmages, directing their curse powers against enemies, for a price.
But the most sought after sorcerers specialize in moving contraband into or out of the astral void, especially that most sought-after magical power source, the astral diamond, known in sorcerer's argot as "ice". If you trade in ice, you're an icerunner.
And that means respect.