The Ink is a recent addition to the city of the Six. It ebbs and flows across the city streets, appearing as graffiti, 'editing' signs and never, ever where you saw it last. A peculiar phenomena, the Ink has been harvested by opportunistic tattooists to create living artwork, forever in (slow) motion across a person's flesh. But given the Ink's ability to avoid people well, who can say it was the tattooists who took advantage.
The Ink seems, first and foremost, to want to spread. Those lucky (?) enough to bear it soon find the Ink in their minds as well, scrawling across their thoughts just as it does their streets; encouraging, cajoling, editing. Sometimes they are seen adding to the city's graffiti, sometimes moving crates in the dead of night and sometimes they are accused of going bump in the night.
The Ink appeared first in the city's outskirts and seems to be slowly spreading inwards, feeling its way to the more regulated and posh inner city streets. Perhaps the Ink is a tool of an older thing, seeking to spread a certain message to the Six. Perhaps the Ink is a warning of things to come, a benevolent entity, only capable of communicating through the written word. Or Perhaps the Ink is a living, mobile censor, eliminating any knowledge it deems 'forbidden.'
Perhaps the most perplexing thing about the Ink is people's inability to refer to it by any other noun, even when they have only seen it once and know nothing about it beforehand. Can the Ink seep into your thoughts before it seeps into your skin?