The Winter Holiday was established in 2957 in honor of the Inter-Faith Congress's one-year anniversary. As with other Unfinished Book Movement celebrations, it was routinely revised afterwards to improve inclusivity and integrate elements of additional religions and traditions. During the Republic era, the Winter Holiday was revised to include elements of Clan Nova Cat mysticism.
The eleven-night ceremony, led by an officiant known as the Reveist, traditionally features an eleven-candle candelabra, the Mastora. It is surrounded with decorations drawn from various winter celebrations, including a garland-adorned evergreen tree, an equally-sized silver pole, and horns of plenty. Each night begins with the lighting of Mastora candles, one on the first night and one more for each night, each candle holding a symbolic meaning.
Each night of the Winter Holiday has its own theme and practices. Recurring practices include celebratory meals, exchanges of small gifts, and the sharing of thoughts and opinions. Of particular note are the fifth and eleventh nights, the nights most commonly celebrated by those who choose to celebrate only one night. On the fifth night, a bonfire is lit, symbolizing conflict, and attendees eat around it as the fire burns. When the fire goes out, two people enter the circle and act out a fight symbolizing death's eventual victory over life. The eleventh night, corresponding with Star League Day, features another bonfire, a present exchange, and a feast, and attendees are encouraged to think about humanity's past accomplishments and future potential.
- Shrapnel Issue #7, "The Winter Holiday"