Longships are a type of boat usually used by kvaldir raiders. The kvaldir can be seen using them to attack the tuskarr city of Kaskala.
The Naglfar, a fearsome ship, is used to deliver cursed and damned vrykul souls to Helheim and the clutches of Helya. Several other longships are also anchored in Helheim.
In the RPG
A longship is a 75-foot-long ship with forty oars and a total crew of 50. It has a single mast and a square sail. It can carry fifty tons of cargo or 120 soldiers. A longship can make sea voyages. It moves about 3 miles per hour when being rowed or under sail.