Doomed by the Shadow…
The Swollen Shadow’s magic is such, that anyone transported to its demi-plane, will always first arrive in the somber and hazy Umbral Fens, which surround the City of Shadow. After some searching one may find the Brittle Road, which leads through the shadow-choked swamps, to the City proper.
A Renaissance dawns. A School of Art emerges.
Some parallel worlds have different time-flows, like the fabled dwelling-places of the elves: those who visit them under the hill for a night return to find that years have passed in this world. Perhaps it is the gate leading between the worlds which causes the alteration. If a gate were 'misaligned', the shift from '| |' to '| \' or '| /' as it were would lead to that difference, much as a light-beam split and bent by a prism ends up taking a longer path. There might even be a mathematical function linking degree of misalignment to alteration of time-rate.