The Jormung is the heavy assault line ship in the Cylon fleet. The Jormung is a popular ship in the fleet due to its massive amount of hull points you can have and its relative cheapness (it costs Tylium to buy). However due to the Armour piercing rounds now introduced, the hull points does not matter as much as it used to. However, It is still a common ship used in Fleet Battles due to its size and weapons.
Sometimes it is also used as missile ships due to its large number of hull points, but that role is usually taken by the Fenrir, as it has more energy.
If your looking for being the last ship standing then this is the ship for you, however it is a massive ship and the turning rate, and overall speed is very slow so it can be eaten alive by strikes and escorts, so always bring a friend with you, an EXPERIENCED friend.
"The largest abandoned ship class so far recovered by the Cylon Fleet, the Jormung's massive wedge-shaped hull is thickly armored and heavy braced, offering superior protection from enemy fire and allowing the ship to act as a mobile fortress on both offensive and defensive operations.
As a heavy assault vessel, the Jormung can be equipped with more hull systems than other line ships, further increasing its toughness and defensive capabilities."