The Painters Guild is another boring professionals organisation, that trains apprentices, and organizes a feast&dance celebration once a year, plus the usual small politicking.
And as you surely expect now, it is a facade.
The “Shadow” or “the Night” is a power that many fear, said to have fanatical followers, delighting in terrible rituals, but luckily living in remote areas, where they stalk upon unwary travellers, etc, etc, etc.
Followers of the Shadow are Illusionists; there lies their main power. While they are all priests to a little degree, they are really wizards, common magic-users. Since there are so few believers, their god has little of mortal magic to give back. They gain no special powers, but they know that sometimes… if an illusion is particularly well-created, or its creator in great need, their god may transfer some power into it, making it more… REAL. If an illusion cannot really harm anyone, it could then, or it could gain actually a mind of its own, or last much longer, and be surprisingly hard to see through.
The Painters Guild is their cover, a way to find new students. As shown above, they search mainly among the poor folk, a coin disguised with a crude illusion may suffice. Few people manage to look past it, and if it is placed well, talented children may be found. (Needs some means of spying though.) Later come the recruiters, they simply let children paint something, and offer them teaching if their paintings are interesting (or are marked as having potential). And what parent would deny its child basic education, learning a trade, complete with food and lodging, with a possibly great future?
Painting (or drawing) wasn’t chosen accidentally. An artistic pursuit, it teaches one the need for details, to look carefully on the world around, and other things important for creating illusions. Throughout the study, they are carefully selected, and later offered another kind of training.
Many of them become good, or at least mediocre artists, that can sell their works with some success, and a little illusion can make their works seem even better, for a while.
Their morals are, well, somewhat dubious. While they strongly reject stealing, they argue that lost things belong to no one, and can be therefore safely claimed. Some actually try to arrange for things to “get lost” or “forgotten”, and take them, but that is discouraged. The problem is that the loosing person must know the object is lost.