Masser (RS 8409-1792-6-147564-400 1.2 in SE 0.9.7.4 patch 5) is a cold S-Class world that was colonized by the Mercurians. Masser orbits the temperate O-Class planet Nirn, together with a D-Class world called Secunda. Masser's populace live in large domed cities inside craters, as well as the massive underground cave system called the Dweech. Masser's inhabitants look similar to bats and use echolocation to supplement their sight, and as such are known as the Echmer or Echo Folk.
With a diameter of 2847.2 km, Masser has a very low gravity at only 0.09 G. It is tidally locked to Nirn and orbits at a distance of 64025.1 km once every 2.8 days. The moon, along with the entire binary star system is only 2.2 billion years old. The average temperature is a frigid -88.4 °C.
Masser's terrain consists of several regions. The largest is the upland region known as the Hae'macrin. Hae'macrin is often covered in water ice, and the peaks are rich in the mineral Euphrite. The lowlands of Opal are tinted blue do to the presence of unicellular bacteria there, and are rich in the mineral Solarite. The third region is the caverns of the Dweech, a vast and alien underground cave system home to the Echmeri Urbs.
The Echmeri live in two primary types of settlements, the Domed Craters and the Underground Urbs. Most craters on Masser are covered in a large dome, and house a city inside them. A small region of the Opal is home to the largest Dome, a cyberpunk-esque megalopolis called Tomorrowind. Domes typically have modern or futuristic architecture. such as large towers that hold up the dome or entirely glass spheres containing housing. The Urbs, however, are much more steampunk-looking, having facilities to process ores and nestings on the roof of the cavern. Urbs have architecture focused on geometric shapes and sharp corners, although Oexra'numsaz, the Echmeri capital, has more futuristic architecture.
Echmeri culture centers around pragmaticism and logic, and the Echmeri worship no gods. However, they revere their founder Hrandeil, who built the great space station known as the Pleonastic Spire by hand. Otherwise, culture has many differences depending on whether they live above ground or below, and also differences between each Urb and Dome are common.