Ships of the class were comparable in terms of size to the Galactic Empire's Imperial-class Star Destroyers and were armed with two powerful fire-linked guns fixed to the forward hull which fired a large ion pulse followed by an enormous, spiraling plasma shot. The ion shot disabled the shields so the plasma shot could do maximum damage. They were also armed with turbolaser batteries in their wings. However, once the main cannons were destroyed, the ship is nearly helpless against conventional capital ships with only one turbolaser battery on each side.
In addition, they could bombard enemy ground positions from orbit with their devastating weaponry. It was a very strong—and very expensive—warship.
Although the class had heavy armor, they were cumbersome in battle and needed protection from quicker capital ships and their starfighters. These ships were known to utilize their self destruct mechanism when it was required to damage the enemy in a losing battle.
The ship that would become the Aggressor-class was designed by the Galactic Empire at some point prior to the Battle of Yavin. The plans were kept onboard the first Death Star, where they were being studied, along with other new ship designs. Upon the station's destruction, the plans were safely stored in a data pod, which was located by Tyber Zann after the battle.
Zann stole the prototype vessel from the Empire and modified the plans to create his flagship, the Merciless. Other Aggressor-class destroyers built after this were based on these modified plans. They soon became part of Consortium navies and proved effective against other capital ships but vulnerable to fighters. During their service to the Consortium, they also became well known as "Underworld Capital Ships".