She was considered an improvement on the Skorpionen class of monitors, with heavier armour and a wider beam.

Thor was armed with two 10.5 inch rifled muzzle-loading guns in a revolving turret.

On 7 March 1919, while being towed to the scrapyard, the ship was caught in a storm that broke the towing cable, stranding Thor on an island outside Verdens Ende in Vestfold, and killing two crew members.

A salvage operation removed parts of the ship, but the wreck remains largely intact and now lies at a depth of 8 to 14 meters southwest of Verdens Ende.

[1] Thor is one of only three accessible monitor vessels in the world, the others being USS Monitor, which lies at about 60 meters some 42 kilometers southeast of Cape Hatteras, North Carolina and HMVS Cerberus, in 5 metres of water in Victoria, Australia.