The original definition of eresian is a gender that is a combination of lunettian and mercurian. It is also known as merlunettian. An eresian person may feel both at once or they may be fluid between them. They may feel different amounts of each gender at different times.
Under the rework of the celestial gender system eresian is a defined as a gender that is plutoian, lunettian, and mercurian. Someone who is eresian could feel all genders at the same time, feeling a connection to soft feminine energy, soft gendered energy, as well as a connection to the void. Or they may be fluid between them. They may feel different amounts of each gender at different times. Eresian can also be considered the demigender form of venusian.
The term ceresian and the flag were created by Tumblr user Juparian on December 31, 2017. However the definition of many of the celestial genders were altered in a rework by Tumblr user System-Lgbt reworking the system, to make it more consistent. The colors of the new flag are based off the colors of Eres.