Glowing berries were a specialty of the Silver Moon Tree Court. Because they were difficult to store, they could basically only be found locally within the court. The darker the surroundings, the brighter these berries would glow.
They could also serve as streetlights at night... the Silver Moon Tree Court didn't use oil lamps.
The berries were sweet, could regulate the qi, dispel dampness, and resolve phlegm. They were easy to digest and could both fill hunger and quench thirst. While abundant, they were not the primary food of the Elf Clan.
Because... the glow emitted by the berries would gradually envelop the individual consuming them, imparting the glowing trait — literally glowing.
In other words, after eating them, one's body would emit a faint luminescence. The more one ate and the darker the environment, the more intense the glow would be... It looked quite pretty, but it was somewhat embarrassing.
"Yila... you tricked me~"