Byatis's unique spellbook allows it to sucker in nearby enemy cultists to capture or kill, so not moving isn't so terrible then.
Tzulscha's unique spellbook turns the normally costly Ritual of Annihilation into a source of power instead—but the ritual grants you no score as a result.
These two are the Great Old One Nyogtha, the serpent twins. Even while separated across the board they can still act in concert—whenever one takes action, the other may perform the same action for free; and if one is engaged in battle, the other gets to declare a battle for free.
Nyogtha's unique spellbook allows the second 'head' to be reawakened on the cheap if it gets killed.
Gobogeg's unique spellbook is very meta: Whoever controls him at the end of the game gets to choose all factions, expansions, and so forth for the next game.
Gnorri's (snake demons) are Doom generators. More of them in play, more bonus Doom points.
Moonbeasts (toads?) are disruptive little buggers, and when first summoned are placed on an enemy spellbook, negating it for a turn, or until they pay a Doom to remove it.
Gugs (the gorrilla-esque monsters) are cheap, major combat dice—but they're clumsy, and cannot capture Cultists.
Ghasts are horde monsters, good only for capturing Cultists or soaking damage. That said, when summoned, you always summon all 4 at once.
The Watcher is much like the Bhole from the Dreamlands—just much scarier. If the Watcher is awoken, he attacks the Green Pyramid area, once per player in the game, and cannot be permanently killed.
The 3-5 player board is 20" x 20", the 6-8 player board is 24" x 24", it might not sound like much, but it increases the play area per board from 400 sq in to 576 sq in.
The book itself is an excellent resource (as it should be), the rules layout is clear and easy to understand, while there are also lavish illustrations and artworks throughout, along with pictures of all the shinies. (Sadly no gallery of painted sets—but hey, can't have everything).
Art/summary page for The Sleeper faction, showing Tsathoggua, tips on stopping Sleeper, and their victory/epilogue brief.