Alstrium is a Xenogender for those who feel disconnected from all aspects of from the gender binary, but possess an essence of androgyny that manifests in a celestial, ethereal, or otherworldly way, regardless of Assigned Gender.
The name Alstrium is derived from the Latin root word aster, meaning "star," and inspired by the English word astral which means "of, relating to, or coming from the stars."
Alstrium is an androgynous variation of the original gender, Aetherium. All genders in this family describe not just a connection to heavenly bodies and the otherworldly as gender, but as feminine, masculine, and androgynous presentations of that gender. Alstrium specifically, however, exists as both a combination of the feminine and masculine, and exist as it's own presentation entirely.
Before being officialized with a name or flag, Aetherium was simply referred to as Calliegender, as a sort of running joke to play on the indescribability of the creators gender identity. It's first proper dedicated conceptualization was in the form of a starter pack image. Several months later, the creator Calliope made and published the official gender and flag, first in its Discord server and then immediately after on their Tiktok.
After making Luminium in response to being asked about a masculine version, Alstrium was born as a combination of the two, for those who don't feel more feminine or masculine.