Probably need more hints on your story idea. The whole "punishment fits the crime" idea.
1. some manipulation of earth's mantal forces in the area under the city to cause a magnetic force that attracks a massive reverse polarity meteor, suspending the sun rays from reaching the land below. Adds the added dimension that when you shift it, it lands on the next city, or shut the one off in the mantal and see squashed city. Assumes you can walk out from under it, into the light.
2. Transport the entire city to the dark side of the moon it resides on, which like mercury does not rotate.
3. Give a Jupiter eye a permanent location over the city.
4. Drop the town down a sink hole of massive proportions after encasing it into an globe of containment.
5. Cause a rotating planet to freeze without losing it's orbit....permanent dark side.
6. Transport the city into the future beyond the return of the Big Bang where all matter disappears, again contained in a sphere of some sort. I think I might have kyped that from an outer limits episode, but I hated them and I've never watched any reruns, nor DVD.
7. Transport it to the dark side of Mercury, provide means to contain the atmosphere.
8. Drop it, Atlantis style into the Deep Trench of the ocean, another container devise.
9. Giant planet eating monster, drops a pile on it. contain it.
10. Industrial Waste gasses black out the sun, same force disrupts the atmosphere--stopping all wind circulation.
Poster Darkling casts a spell creating Dark for all time and sends the channel that shall not be named into it to reside for all time as well. I think that is a layer of Dante's Hell, isn't it.
Enough already..gonna go zap some monsters on guild
give me 20 questions and we'll try again.
uhm, you said high fantasy.... race that spread a micro thin filament over the city, collect sunlight to power something, stealing energy from the power plants of the city etc..
Your post request is a disease.... So a form of bioengineered insect or space travelling spore that eats sunlight, stealing it away. Or an airborn virus that mutates creating a sticky soggy mess that lies between the layers of the stratsphere and hardens to steal strength with zero weight so it remains suspended there.