These models were made with MATLAB R2016a from the data and observations of the fifth mainline game of the saga The Elders Scrolls V: Skyrim. The objects modeled were Nirn, also named Mundus, the planet where the TES saga take place; Masser, Jode or Mara's Tear, the red, Mars like and apparent bigger moon of Nirn; and Secunda, Jone or Shandar's Sorrow, the gray, Enceladus like, smaller moon of Nirn. Nirn was made with a elevation map of Tamriel found googling it, that I cannot found the original source, the other continents of Nirn aren't officialy mapped, even the contour. Masser and Secunda were made mapping the original textures from the game to spheres coordinates, mixing the different views generating a global texture. Finally I applied various filters to get something like a topographical map that I used to generate the 3D model in the same way that I made other astronomical bodies. The three bodies were scaled to one in sixty million to make them comparable with other bodies of similar size. Secunda, because of its small diameter, is scaled also one in twenty million if you want to make a more detailed print, but of course, it's not in the same scale of Masser and Nirn.
The file's names explained: name_1_x_10_y.stl is 1 : x * 10y. So _1_6_10_7 is 1:600000000 or one in 60 million.
The size of Nirn was taken from the interpretation of this post, and it is 68% the Earth's diameter, about 8665 km. He compared the separation between the biomes of Earth with that of Nirn. Then extrapole this distance with the sizeof the region Daggerfall, that is about the size of UK.This is true assuming that the size of the gameplay set in TES II: Daggerfall is the real size of the region. This was probably the intention of the developers, because it is a huge area for a game. In later games the playable area was seriously reduced to a more normal one, in order to make it more detailed and less tedious to travel. In TES V: Skyrim this area is reduced a lot, but it wont be consider as the real scale
The size of Masser and Secunda
The size of Masser and Secunda was calculed with the data and observations from TESV: Skyrim, but not from other games. This is because it was the last game released of the saga, and some details contradict that of other games. For example, contrary with that many think, Secunda does not orbit Masser, but it does around Nirn. If you go to a clear plain in Skyrim, and wait (command T in PC) until the hour 20:00 to 22:00, you will see Masser standing in the sky (if it is cleared) at one point. Then, if you wait again 24 hours you will see it at the same point every day at the same time. This is compatible with Masser being locked in a Lagrangian point, but the configuration is not compatible with it having lunar phases. You could see in the game, a new moon phase of Masser or Secunda at midnight, which is impossible. However, if you wait every 24 hour you will see Secunda moving near a ecliptic plane, in the direction (but faster) that the sky does, leaving Masser from the right side and reaching it on the left side, which means that it is in a retrograde orbit. Every five days Secunda makes a "conjuntion" with Masser, and both moons complete each phases every five of these conjuntions. The direction in which the sky and moons moves is different of that the "sun" Magnus moves, which is impossible. For the orbit period calculation I've considered the moons phases of Masser like its period, with the moon moving in prograde orbit around Nirn. With this Masser makes an orbit in 25 days, and Secunda does in 6,25 (because it makes 4 orbits every Masser's orbit).
In order to know the diameter we could measure the angular diameter, comparing with the zenith-horizon angle (90°), I've measure that Masser is four times smaller than this angle, that is 22.5°, 45 times bigger than that of the Moon seen from Earth (which is nearly 0.5° or 30'). If it is so, and the distance Masser to Nirn distance is the same of that of the Moon, Masser would be larger than Jupiter. However, most of the games in which the Earth's Moon appears, it's exaggerated compared with the real one. For example, in Fortnite, the Moon is 20 times smaller than the horizon-zenith angle, 4.5°, 9 times the real angle diameter. I'll take this as a "game aberration" as a direct factor of 9. With that in mind, the new angle of Masser is 2.64°, and Secunda's one is about 2.2 times smaller, 1.2°.
Finally, we can obtain the diameters of the two moons using the eccuations of gravity acceleration, tangencial and rotational speed and angular diameter; considering the uncommpressed density of Nirn, Masser and Secunda 3 g/cm3. The resultant diameters are: 8832 km for Masser (~69% the size of the Earth), and 1593 km for Secunda (about the size of Rhea).
Masser (red), Secunda (white) and Nirn (blue) in the same scale. Made with Microsoft 3D Builder.
Simulated view from Nirn (blue), of Masser (red) and Secunda (white), with the size and the distances calculated. Made with Microsoft 3D Builder.