From around 1915, plans were made in Saxony to procure heavy express locomotives, which resulted in the XVIII H for flatter routes and the XX HV for routes with longer gradients. The model for the former was the Bavarian S 3/6, after a locomotive had been loaned for testing purposes, but no series production had been started.
Like its prototype, the XVIII H had the wheel arrangement 4-6-2, but in contrast to this and its larger sister, its power plant consisted of three cylinders with single steam expansion. For the first time in Saxony, a wide firebox was installed above the frame, which was placed behind the coupled axles and in front of the trailing axle. All three cylinders drove the second coupled axle, but for reasons of space the middle one had to be installed a little higher and therefore inclined. As with the XX HV, a relatively modest size of 1,905 mm was chosen for the coupled wheels. However, since the running characteristics were good because of the leading bogie, the top speed was set at 120 km/h right from the start. The running gear was constructed exactly like the other Pacific locomotives, with the front bogie being laterally adjustable by 38 mm, while the rear Adams axle was adjustable by 60 mm. The deceleration took place on one side on all coupled and running axles.
While the XX HV was mainly used on the routes towards Franconia, the XVIII H was mostly used in the lowlands. This included above all the route between Dresden and Leipzig or the connections in the direction of Berlin or Breslau. In 1925, all ten examples were taken over by the Reichsbahn. Within the class 18, which was intended for Länderbahn express locomotives with a 4-6-2 wheel arrangement, the Saxon machines were given the numbers 18 001 to 18 010. Later, all locomotives except for 18 002, which was lost in the war, came to the GDR Reichsbahn and stayed concentrated in the Dresden area. Their end came between 1965 and 1968.