The Pilgrimage is the Coronation of the Emperor/Empress. This is the one time per year that all of the Wandering Ronin chapters strive to get together to celebrate the game and enjoy each others company.

Summer Solstice Celebration (The Pilgrimage):

An annual event hosted by the Imperial Officers with assistance from the whole Empire, this is the once-per-year event that allows all of Wandering Ronin to get together under a common banner, celebrate the anointment of the new Emperor or Empress, and show off who you are and what you have done. A chance to make new friends and alliances, get re-acquainted with old ones, and become part of the spectacle that is the Imperial Coronation.