Time always flew when he was learning. Yun Province's climate made the seasons hard to tell apart, too. One day, while Pan Long was sketching on the street, he happened to see several old men wearing nothing but white cloth carry a jar larger than a person toward the village outskirts. People avoided them as though they were plague gods, keeping at least ten paces away. Only then did it dawn on him.
"It's the Dragon Boat Festival again!"
The custom of cultivating Gu still survived in many parts of Yun Province. The most common method was to put several kinds of venomous insects, each fed secret medicines for some time, into a jar on the day of the Dragon Boat Festival, then place it in a specially prepared underground chamber. The cultivator would pray to it regularly, whether every two or three days or every five or six. This continued until a cloudy, rainless day in midsummer, when the jar was opened at noon, with neither rain nor sunlight in sight. The venomous insect that survived inside was the so-called "Gu."
This kind of Gu was not particularly poisonous. Its main use was rather interesting: it served as a witness to oaths.
Specifically, the Gu was fed the cultivator's blood. After about three years, it would gain spiritual awareness. If someone later needed to swear an oath, that person and the cultivator each gave the insect a drop of blood, and the person made the Oath before them both. If the oath-maker broke their word, they would inexplicably die of poisoning.
As for how that poison worked, opinions varied.
Some said the Gu gained spiritual awareness, knew the person had broken the Oath, and went to bite them to death.
Others said that once the Gu ate a drop