World Encyclopedia: Games and traditions
Winter Solstice
The shortest day of the year. The school closes for a fourteen-day holiday, when most students travel home, and the river keeps shrinking towards New Year.
The River
The river in front of the castle grows narrower all autumn and is at its narrowest on the last day of the year.
On that day, some people walk across it to show that they can. It has been that way for hundreds of years. Ahra’s brother Maka says you can walk across it if you are foolish enough. He did it himself the year before, and afterwards his ears rang for an hour.
The Last Outing
Before the holiday, all the years make one last trip to Tés Aváir. The stalls in the market square open again for the occasion and smell of roasted chestnuts, hot apple cider and mulled wine. It takes place on a Wednesday in the second week of December.
The Holiday
The winter solstice holiday begins on a Friday and lasts fourteen days. Nearly everyone goes home, and when the last student has gone, the castle falls quiet.
Spoiler (revealed in chapter 23)
Ahra overhears a conversation in the passages: whatever is locked away beneath the mountain is held back most weakly at the winter solstice, when the power in the earth is at its lowest. Just as the river is at its narrowest.