D&D 5E: Grim Hollow: Saga of the Seasons

Saga of the Seasons is a 240+ page campaign-length adventure covering level ranges from 3rd to 11th level, that lasts an entire year in-game, taking players through the four seasons of the Valikan Clans.
It gives the players an adventure that shows “A year in the life of a Valikan Clans viking group”. This book includes monster stat blocks and shows examples of how to implement the Raiding Mechanics detailed in The Raider’s Guide to Valika book.