Five new scenarios and eleven double-sided board tiles are included but it appears no new monster of investigator miniatures this time out when Call of the Wild releases.
From FFG:
Call of the Wild, an expansion for the Mansions of Madness board game, sends investigators into the wilderness with five new scenarios and eleven double-sided board tiles. Investigators are plunged into the mysterious backwoods, shaking the foundations of what players have come to expect. What’s more, the keeper must solve puzzles and seek out clues, a focus on outdoor maps encourages non-linear exploration, and Allies assist in combat and driving the macabre narrative.
The stalwart investigators have taken to the woods to uncover the secrets behind all new macabre mysteries. The terrain that must be traversed is vastly different from the interior of the mansions, crypts, and laboratories that players are used to encountering. The wide open spaces of the outdoors allow for a new kind of experience in investigations.
Exploring the Fetid Outdoors
Exploration is key when dealing with the uncharted wilderness, and players will have to put their sleuthing skills to the test as they wander the forested countryside. Clues no longer need to be gathered in a particular order, and players must assemble answers from the information they uncover as they make their own path through the darkness. This new approach to exploration allows the story to unfold in a totally non-linear fashion, introducing whole new modes of storytelling for Mansions of Madness.
Investigators must take care as they search, for the forest and swamps can be as unforgiving as the horrors that prowl its depths. Hidden pitfalls will injure heroes as they seek out information, and rushing rivers can frustrate their progress or trap them with some undesirable company. Clever players can find ways to turn the terrain to their advantage, however. Boats and bridges can manage the muck, and getting on the right side of a body of water can help an investigator make the 
most of using his ranged weapons.
To aid in their investigations, players will come upon an array of Allies while wandering the woods. These new Ally characters are specific to the stories in Call of the Wild, and each one has his own deck of special cards. Allies work as neither investigators nor monsters, but can participate in combat, have conversations with investigators, give special tasks to complete for rewards, or even be driven insane by contact with the horrific creatures that stalk through the forest at night. But beware! Insane Allies fall under the control of the nefarious keeper, so investigators would do well to shield their helpers from the more mentally disturbing encounters.
Rituals and Secrets, the Keeper’s Dark Work
The investigators aren’t the only ones who will have to contend with new challenges in the great outdoors. The forest is a friend to no one, and the keeper can have his plans frustrated by industrious investigators who use the environment to their advantage. In some scenarios, the keeper must solve ritual puzzles in order to complete his dread plans. Gathering the arcane items for the ritual can be a challenge in and of itself. Depending on the story, the keeper may need to search the map for items that have been hidden from him by the investigators.
The keeper is not without new tricks, though, as the use of the Keeper Action cards in Call of the Wild works differently than in the base game. Keeper Action cards are now chosen from an assortment offered to the keeper at the outset of a game. Crafting a powerful and customized hand allows the keeper to base his strategy around his unique style of dastardly gameplay. Also new to Call of the Wild, the Keeper Action cards all have the same backs, meaning the cards in the keeper’s hand are not revealed until he uses them for the first time. The keeper can develop a strategy around retaining his cards until he finds the right time to strike and destroy the hopes of the investigators, adding an extra level of tension!
Look forward to marshaling your Allies, guessing at the keeper’s cards, foiling or completing rituals, and exploring the great outdoors. With all of these new challenges to contend with, the keeper and investigators alike will have their hands full as they contend with the terrain and terror of Call of the Wild. Look for this expansion to be released early in 2013!
