From the introduction:
This adventure is designed for a party of six to eight characters. For smaller groups, the number and power of foes should be adjusted accordingly.
A year has passed since the attempted Rise of the Underfolk, and Sparrowfell is now at war with itself. Everard Arbonne, having revealed himself as a dreadful Power in his own right, has found allies: The Queen Thrice-Cursed, the Thornéd Lord, the Heavy-Handed God and the Dog That Ate the Moon, just to name a few.
Sparrowfell has rallied its own champions: The King Clad All In Copper, the Incurious Man, the Uncast Shadow, the Speaker of False Truths...and perhaps the PCs, now renowned heroes in their own right.
They may not be enough. Everard has become an Ouroboros, metaphysically consuming his alternate selves and adding their power to his own, and is planning a feast beyond measure.
Unless the party can stop him.