Oslog is an original song from the TrueDark Rising world. It belongs to the early years of Farshadow, when a great white-furred creature patrolled the forest and shoreline at the Crossing, and the Kinsfolk slept because he stood there.
The companion story remembers Oslog as large and heavy, with arms like fallen trees and hands that knew how to close. He did not chase for sport -- he hunted. The things that crawled up from the earth did not crawl back down on their own. Oslog crushed them into the soil until the ground remembered how to stay still. What shone on him was not his own light but what the dark had failed to swallow -- moonlight, firelight, bioluminescent spores clinging to his fur from the glowing waters where he bathed.
The people built near the lake because Oslog walked its edges at night. Children slept while he was awake. One winter, Oslog went deeper into the forest than he ever had before. The dark had gathered there. He did not come back. The elders say he did not leave the people -- he went where the dark was thickest, so it would not follow him home.
Like all songs of this world, it serves as memory. It is meant to be sung with weight, and understood fully only in hindsight.