For anyone who needs a monster, here's the beaut I'm including in my demo game.  Yes, it is HEAVYLY influenced by the lobstrosities in Stephen King's Dark Tower books.  That and the critters from Attack of the Crab Monsters.  And who can forget the giant crab from The Mysterious Island? Keep in mind, I'm expecting something in the neighborhood of 10 players for this game.  You may want to tone it down a bit for smaller groups.

The ground shakes as a monstrous creature rises from the sand and scrub.  It appears to be a massive crab, nearly 18 feet in diameter, with a purplish gray carapace atop which sprout patches of quartz-like growths.  It has two sets of claws, one pair massive and blunt, the second small and serrated.  Its face is vaguely human, as though a man’s face were grotesquely stretched across its shell.  Under this it sports a prickly, coral-like beard.

Crabstrosity

Strength 15

Monstrous Powers:

• Massive Claws (Str 5): this creature has two massive claws that make it a greater threat than it would otherwise be. Each claws is treated as an individual monster (Strength 5), and can be destroyed by inflicting a single Dramatic Wound.  Spend a Danger Point when a target suffers a wound to have the crabstrosity pin the target and draw into range of its bearded (and poisonous!) mouth.
  • GM Note: By spending 1 Raise, a hero can engage these claws while avoiding the crabstrosity. 
• Razor Claws: The smaller set of claws near the crab’s face are razor sharp and serrated, capable of slicing a man into small pieces. Spend a Danger Point to double the number of Wounds dealt by the Monster after a successful attack against a Hero.  Pieces torn from heroes are immediately devoured by the crab.
• Chitinous (Outer Shell): Spend a Danger Point to negate all Wounds dealt to this Monster by a single attack.
• Venomous (Beard): Spend a Danger Point at the beginning of the Round. When the Monster deals damage, remove 1 Raise from the Monster’s target.
• Questions: The crabstrosity constant murmurs sound like nonsense questions (“Dad-a-chum? Dum-a-chum? Ded-a-check? Did-a-chick?”).  The constant refrain is confusing and maddening (1 Raise or lose a die for the next action).
• OPPORTUNITY —Weak Spot (Soft Underbelly): When making attacks against the crabstrosity’s underbelly, a hero may spend a Hero Point to add his/her Brawn score to any wounds cause by a successful attack.

Edit: Oops!  Forgot to add the description.