Opheros, the Heart of Sacrifice

Opheros is the Sarnian name for Impera's moon, although the term is used by almost all societies on the Continent. Hailed by the Sarnians as the heart of the god of sacrifice, brother to Eulus, the sun, and their national god-patron, Opheros is a very important celestial object not only in Sarnios but also in the rest of the southern continental kingdoms.
According to Sarnian myth, Eulus and Opheros were the two godly brothers ruling over light and warmth. While Eulus was always the stronger and more hot-blooded, shining a bright golden and battling the Beyond with his thousand spears, Opheros was the calm, collected brother, whose silver shine was weaker and less warm, but his insight and heart easily outmatched that of his brother.
The two brothers would be tasked by Anthos, the Creator god, to safeguard the world from the all-encompassing darkness of the Great Dark Beyond above it. Splitting up time so that they can rest while the other guards the heavens, the brothers would patrol the fragile boundary between Impera and the Beyond and sleep at opposite times. However, soon Opheros was unable to defend his domain as effectively as his brother and would fail to light up the sky, barely managing to protect the mortal realm.
Getting pummeled by attacks again and again, Opheros would be at his full strength only one day in a month, otherwise constantly declining or regenerating from his wounds. Soon enough, darkness would seep through the skies and Opheros would barely be able to stop it. Facing a particularly large attack that he knew he could not stop, Opheros would do his duty and sacrifice his life in order to keep the world safe - he would tear his own body apart, scattering his remains over the entire night sky as stars, his shine spreading out and resisting Beyonder incursions like a net of divine power and selfless purpose. The only part of him that did not fall apart was his heart - scarred by his violent sacrifice and battered by constant stellar assault, it continues his old routine in the sky despite his life force being all but spent - fulfilling his duty even after death.
The story of Opheros represents many core values of the marital Sarnian society - duty, sacrifice, temperance and discipline. These values make him the chief deity despite being the weakest celestial in Sarnian myth, celebrating the value of virtuous and selfless behavior regardless of one's personal power or capability and in the face of any foe, no matter how superior.

Geography

Opheros is relatively large and well visible from the ground on almost any clear night. Its shape is circular and it is marked by craters and canyons, as well as a huge rift from its northern pole almost to the equator.
It orbits Impera every 18 days, which is generally considered the length of a month in most cultures on the Continent.