Boreas Dimension
Boreas is one of the Splinter Realms.
It was originally ruled by Ikthalon, the avatar of stagnation and resistance to change. He was defeated by the mortal sorceror Watoomb, who was seeking to become a Principality (a Lord of the Spliter Realms) as a means of attaining immortality. After his victory, he ruled the dimension with his wife, Umar the Unrelenting.
Geography
Boreas takes the form of a massive city, built of grey granite-like stone. Much of the city is uninhabited even now, and it is unknown when or why it was built. It has been theorised that the city pre-dates the splintering of Subwhere.
Ecosystem
Under Ikthalon's control, Boreas was a realm of ice, where nothing grew and only Ikthalon himself could thrive. According to legend, it was so cold that even magic would freeze.
Since his defeat, and the removal of his inertial influence, the plane has warmed considerably, and now supports a population of sapient beings. Plant life exists, although due to the cold damp climate and the urban environment, it is primarily varieties of moss, lichen, and fungi, many of them with powerful magical properties.