The Dark Ritual Stretch Goal box is included in the original Kickstarter Dunwich-pledge. It includes rewards for the base game as well as the Blood Ceremony expansion.

Thus far it contains:
3 Monster cards
Priest card
Ancient Cult Board
22 Atomic Resource Tokens
6 Three-value Atomic Resource Tokens
Windwalker Cult Board
3 Glacier cards (Wendigo, the Gnoph-Keh, and Rhan-Tegoth) Box Art may differ from that shown.