Bifrost

In the Aeon of the Champion story series, Bifrost was the golden bridge separating the Kingdom of Terris Aurum, a floating island nation founded by the Watchers, and the rest of Middle-Earth - a single supercontinent known as Old Vigrith. The Watchers rarely used it themselves; it was a means of banishing someone from the kingdom permanently. For this reason, Bifrost is longer on one side; the bridge is crossed more quickly when leaving the island than coming in. Bifrost is also extremely long in and of itself, and contrary to popular belief, does not run in a straight line, but has various twists and bends to its pathway.

The Nephilim scaled Bifrost in order to reclaim the kingdom they held perceived inheritance over, in a war against the watchers several years before the Second Sin War.