410A.D, the Visigoths started their invasion on Rome by starving them. Rome's foods and arm supplies were cut off by the Visigoths and were weakened so that the planned invasion would succeed for the Visigoths who were looking for food and treasure. Due to the lack of food supplies, soldiers were way too weak to defend themselves and the country. The Roman Empire fell, causing massive amounts of casualties. From a knight's perspective, this was considered as “dark”.
Life was at its darkest moments when a massive killer, the Justinian Plague, outbreaks in the city of Constantinople in 541A.D and swept through the east Mediterranean population, killing a quarter of the east Mediterranean population, resulting thousands of bodies piled around the city. This proved to be one of the darkest periods during the Dark Ages. From a knight's perspective, it is definitely "dark". The plague was named after an Eastern Roman Empire, Justinian I, who was in power during the initial outbreaks of the plague. While he almost united Rome, he died of the plague.
There were many battles that influenced a lot on the world today, for example in 732A.D, Charles Mortel lead and took the first victory against the Moors, stopping the Muslims to advance further. But since there was plenty of blood and gore included, this was only considered as slightly "light".
In 793A.D, the Vikings landed their attacks and invasions on England, causing enormous amounts of casualties, since no one knew how to fight a war on sea. Until 871A.D, Alfred the Great built fortresses that prevented the Vikings from damaging from the shore. The Vikings stopped their attacks until 900A.D. For a knight, this was firstly considered "dark", then "light".
During the period when Christianity was a major influence, Christianity was basically the last hope for everyone, due to that fact, kings are extra likely to unite and conquer, meaning they are more likely to return with victories. For example, King Clovis used Christianity as a source of hope, motivation, and in the name of God, he united the Franks during 511A.D. Without Christianity, without any hope, Europe would’ve collapsed long ago, and the dark ages would be the last period in Europe history. From a knight's point of view, this was considered as "light" for them, because by using religion as a source of hope and motivation, soldiers are often more unified to fight as one in the name of God.
Although when the topic “How dark were the dark ages” comes, majority of the people think of chaos, wars, deaths, darkness, but for a knight, it wasn't "completely" filled with darkness. Yes, there were less bright sides than the dark sides during this era, but there was still a significant bright side that kept the Dark Ages balanced, Christianity, the hope that kept the motivation and the spirit going.