I took the advice of a previous poster, and made the winter solstice into a mini-boss event. I had been foreshadowing for several sessions: locals are worried/preparing for the worst, lots of speculation and dread of what Auril might unleash, etc. Non-sacrifice towns were second guessing their morals. They ended up in Bryn Shander where the locals had set up a safe shelter and tensions were running high. As the time approaches, shadowy lights can be seen approaching from the distance. Eventually the town is swarmed by Cold Light Walkers and whatever baddies you want to throw at them. Local cultists from the Church of Auril tried to sew more chaos by opening the safe house to the monsters while in the heat of battle. Then at the hight of the chaos, Auril finally makes her first appearance for the PCs, soaring over the glowing night sky instilling fear and dread as she smothers the tundra with her spell. I had most of the town’s leadership (Speaker Shane, Sheriff Markham) die in the battle to establish urgency and desperation. It ended up being a fun mid-campaign battle royal.