The phrase "a darkened side" is correct and usable in written English.
It can be used to describe a part of something that is obscured or lacking light, often metaphorically to refer to negative aspects or hidden truths.
Example: "Every story has a darkened side that reveals the struggles and challenges faced by the characters."
Alternatives: "a shadowy aspect" or "a hidden side".
A darkened side gallery includes three small tabletop fountains whose sprays and drops of water are reduced to crystalline slow-motion by strobe lights, a bit of kinetic art that recalls the historic stroboscope photographs of Harold Edgerton.
It was a ray of hope slicing through a darkened side of Manhattan: Mayor Michael R. Bloomberg's statement in a Friday afternoon news conference that Consolidated Edison could have power restored in most of Manhattan by on Sunday.
In a darkened side gallery, Mr. deSoto's large and beautiful model ocean liner with illuminated portholes drifts slowly and mysteriously around the room, every so often producing its own fog bank (Johnson).
I knocked on a darkened side window and pulled the door open.
"The only time I ever bought coke off of Russians, it was here," he'd told me as we pulled up to a darkened side street lined with menacing clapboard terror-cabins.
As well as a dead Mechanoid from the serial "The Chase" seen from a few long shots in the darkened side of the Vault after they first materialize, and before they depart.
Using something like a white reflective surface (poster board, for example) will reflect light onto the darkened side of the face and produce an added depth to your photographs.
Not long after night fell, tribes began drifting in from the darkened side streets, their spy boys and flag boys scouting ahead for the big chiefs.
When this truck drives through the darkened side streets at night you can see the light trace the trees and the houses.
The animal was placed in the middle of the light side of the chamber facing away from the opening toward the darkened side.
During choral scenes the dancers played characters onstage, while a chorus sang from a darkened place in a side balcony.
