I was told this week to write about the Soulless moons, so here is that post. This is a bit of a gray area for me, as I feel that the information below should be correct, but I’m not certain if everything is entirely viable scientifically. My background is as a history major, not astrophysics. I think that, even though it orbits the planet still, Rythellas may show the same face to the sun at all times, since there seems to be a lit side and a dark side. This might introduce some complications to the story’s world, but should be resolved by the time the final draft is completed.
Like I said, much of this is based on logic and not science. If I’m getting this wrong, please let me know.
The world of Soulless, Ilthirios, is the largest part of a three-body astronomical system with its two moons, Cirellias and Rythellas. It is to be noted that Ilthirios is mutually tidally-locked to Cirellias, the nearer of the moons. What this means in terms of viewpoint from the planetary surface is that Cirellias remains motionless in the sky, locked into a stationary position over the Ilthirian equator. Mutual tidal locking infers that Cirellias’s rotational period, it’s revolutionary period, and the Ilthirian rotational period are all equal.
Both Cirellias and Rythellas would be identified with similarities to Earth’s own moon in that they vary from shades of white to gray (Cirellias being a darker gray, Rythellas closer to white), are heavily cratered, and are geologically dead. Although the (mostly) iron cores no longer spin and thus do not create the dynamo effect necessary to produce independent magnetic fields, both do produce magical forces along their equators, perpendicular to the poles. With rotating cores, both moons would produce a “grand cross” effect with stationary magnetic poles and sweeping magical poles. As it is, though, the equatorial magical poles are as stationary as the axises around which the moons rotate.
Cirellias and Rythellas are both of only slightly varying sizes—even in comparison to Earth’s moon—with diameters of just over 2000 miles. Though they are practically twin bodies when viewed from a standpoint outside the three-body system, Cirellias is only about 1/3 the distance from Ilthirios as Rythellas (~65,000 miles to ~210,000 miles), and appears much larger in the sky. Due to reduced distance, Cirellias is nearly nine times brighter at night than Rythellas, even in the Void Moon phase. At midnight (when Cirellias is full), the sky is bright enough to read by, even if one would still need to read text more closely than by sunlight.
Local time in Edaria—directly beneath Cirellias’s positive magical “pole”—reflects opposite time on the Cirellian surface. The Cirellian new moon phase occurs at Edarian noon and vice-versa, with sunrise and sunset reversed as well. Rythellas, however, orbits independently around the Ilthirian-Cirellian barycenter, with a 2:1 rotational ratio. This means that Rythellas shows opposite faces to Ilthirios within a span of 14 days, with a complete revolution and full rotation (relative to those viewing from the planetary surface) after 28 days.
Rythellas has an orbital inclination of approximately 2 degrees, while Cirellias remains fixed at 0. In respect to the sun, Ilthirios holds a 26 degree inclination. This tilt is enough so that Cirellias does not always shadow Ilthirios, with the penumbra going either above or below the planet during the equatorial growing seasons. However, with the tidal locking effect, this does mean that eclipses are a daily occurrence during the two equatorial summers with a true total eclipse during the equinoxes. In fact, Cirellias conceals the sun completely during the eclipses several days before and after the equinoxes but only because that moon is larger than the sun when seen from the Ilthirian surface. As either equinox approaches, the exact date can be measured with instruments based on how much of the sun is concealed during partial eclipses and how far north or south of Cirellias the sun passes. It is also possible to measure dates on the planetary surface as equinoxes approach by measuring at what latitudes the eclipse passes.
Rythellas and the sun appear as the same relative size from Ilthirios, meaning that any native of Earth would witness a very familiar sight when those two bodies align, although Rythellian eclipses are far more rare.
With the tidal-locking effect from Cirellias, that face of the Ilthirian surface is much wetter than the opposite hemisphere, which is dominated by large deserts. Surface oceans are in mostly stable positions in regard to Cirellias, which does not move to generate high or low tides. High and low tides do still exist, though they are conducted by Rythellas and, less so, by the sun. Without the presence of Cirellias, Ilthirios would be perceived as a much dryer planet than Earth.
Magically, Cirellias is the weaker of the two moons, with the pole showering the Edarian subcontinent at all times. This magical showering led to the evolutionary divergence of the erman race, who developed wings with filaments designed to collect and manipulate Cirellian energies. The constant rate of magic provides a stable source for the ermen. Although Cirellias a negative magical pole on the opposite side of the equator (only theorized by Ilthirian astronomers), it never comes into contact with the planet and is thus of little current interest.
Rythellas, however, has a very intense magical field, but the equatorial poles only interact with the Ilthirian surface twice during the course of its cycle. During the negative—Void—phase, the pole dissolves all magical effects on the planet, completely overriding the Cirellian effect. All ermen lose access to the Cirellian magical fields and are rendered as magically weakened as the large majority of their human counterparts. During the positive—Soulless—phase, Rythellas amplifies the Cirellian effect. This induces a frenzy on the ermen race, going so far as to shift their minds from logic and reason to primal fury and thirst for battle. With that mindset and an amplified magical field, a Soulless erman is especially dangerous, far exceeding their normal capabilities. In order to preserve peace, safety, and life on the planet, ermen return home to Edaria for the Soulless night to surround themselves with loved onces in order to induce the Calming—an effect where berserk ermen can turn to one another and sedate their savage natures until sunrise. Reasoning for the ermen’s return to Edaria during both the Void and Soulless Rythellian phases are racial secrets, completely unknown to humans (though they have suspicions).
In societies’ nature to attribute common features to heavenly bodies, so have humans and ermen alike done so with the twin moons. Both agree that the dominant marks on the Cirellian surface resemble a hand, though the perceived fingers are only geological striations (created during the moon’s formation) radiating away from the southern pole. There is dispute over the lit surface of Rythellas, though, some cultures claiming to see birds or trees. As for Edarians, they claim to see a single open eye.