direct sun light: 0h/day
indirect sunlight: quite dim, the window is 10 meters away
temperature: never freezing, never too hot
We tried a Ficus tree (was 50cm and in good health when moved there, survived several months) and a Pelargonium(20cm, not in perfect health but after only 2 days all it's leaves are yellowish).
No shade-seasoning by gradually applying less and less light has been performed. However it's winter so the day is pretty short anyway.
Are there any common plants that would thrive in near darkness?
@Jurp I never imagined indoors-ines goes beyond keeping warm in winter. I should post a question about that!
Epimediums looks somewhat exotic to be easily obtainable in Europe; doesn't matter as You said it won't work.
Here's an idea. Go to the forest. To the darkest part. Dig some weeds up and plant them home.
However I've done that several times with city weeds and they often die. I give them (moderate)sun, quality soil(instead of the construction rubble they were taken from), fresh air. And almost all wilt within a month.