A little light on the Dark Ages
So what were the forms of lighting used by the people of the Dark/Medieval time period?
Most common was sunlight, for the poor serfs and peasants, with windows that were usually openings in the walls, able to be closed off with shutters in the colder weather. Some few were covered with sheets of horn, leather scraped thin enough to allow light to pass through,or in very rare cases, panes of mica -- they would go to bed with the sunset, rise with the dawn -- and other than the fires used for heat, no other illumination after dark, with the possible exception of rushlights (oil-soaked rushes held in metal loops attached to the walls or freestanding) and torches.
Oil lamps of various sorts, ranging from shallow clay bowls with a pinched corner to hold a wick, to glazed pottery with embedded metal holders that sat on metal platforms with polished back surfaces to reflect the flame, were available for those with the means to afford them. And of course, the richest and most powerful (meaning Royalty and the Church) could afford candles, a true luxury. Glass windows were also a rare luxury, something only for the very wealthy and powerful.