Built by the Karjøhansvaern Naval Dockyard and launched on 1^st July 1893, the Æger was an adapted design of the flatirons designed by George Rendel in an attempt to keep the classic flatiron's shape but give it better protection against torpedo boats. She was constructed in steel and run by two horizontal compound steam engines; However, she proved to be more unseaworthy than her pure flatiron predecessors and a sizeable breakwater had to be added around the deck to prevent seas from washing over the bulwarks. Measuring 33.2 metres in length with a 9-metre beam and weighing 420 tonnes, her ungainly, hunched appearance precipitated her nickname "Toad". Her armament consisted of a 21cm, 7cm and two 5cm breechloaders mounted on a turntable giving a firing arc of 250 degrees.

In autumn 1905, following Norway's declaration of independence, she was employed to defend the Norwegian capital against a possible blockade by the Swedish fleet and re-commissioned in 1914 as a harbour-based flagship to guard Norwegian neutrality during the First World War. Her service life was particularly restricted compared to her seven elder sisters who were all converted to minelayers and remained in service in the campaign of April-May 1940 and beyond. The Æger, however, was never fitted out for any other duties and was sold as scrap in 1932.