The Sea of Ghosts is the name given to the northern waters spanning the distance between Tamriel and Atmora.
The sea is part of the Padomaic Ocean, and merges with the Inner Sea along the shores of north-western Morrowind.
For years, raiders would sail south from Atmora to invade and settle in Tamriel. The most prominent being the legendary Ysgramor and his Five Hundred Companions.
Sometime in the late Merethic Era, specifically during The Return, a violent storm (later named Storm of Separation) took place at sea. This was the event that ultimately led to the death of one of Ysgramor's sons, Yngol.
As time progressed, however, the waters became extremely icy and Atmora froze. The icebergs that litter the water have claimed several ships over the years.
Centuries ago, this area was terrorized by pirates led by the fearsome "King of Ghosts", Haknir Death-Brand, and his crew.
With the installment of the Dawnguard add-on, Castle Volkihar is also located north-west of Solitude, the capital of Skyrim.