http://www.youtube.com/watch?v=3hWlXT9HhFA

The Beast from Haunted Cave
Large Aberration (Cold)
Hit Dice: 6d8+30 (57 hp)
Initiative: +2
Speed: 30 ft. (6 squares)
Armor Class: 19 (-1 Size, +2 Dex, +8 Natural), touch 11, flat-footed 17
Base Attack/Grapple: +4/+12
Attack: Tentacle +7 melee (1d8+4)
Full Attack: 2 Tentacles +7 melee (1d8+4) and 1 Bite +2 Melee (1d8+2)
Space/Reach: 10 ft./10 ft. (15 ft. with Tentacles)
Special Attacks: Improved Grab, Blood Drain, Webbing, Frightful Presence
Special Qualities: Dark Vision 60 ft., DR 5/-, Fast Healing 1, Immune to Cold, Vulnerable to Fire, Snow Walk
Saves: Fort +7, Ref +4, Will +6
Abilities: Str 18, Dex 15, Con 20, Int 2, Wis 12, Cha 12
Skills: Climb +8, Hide +5, Listen +4, Move Silently +5
Feats: Ability Focus (Frightful Presence), Improved Web, Multigrab (see Savage Species)
Environment: Cold Mountains or Forest
Organization: Solitary (Unique?)
Challenge Rating: 5
Treasure: None
Alignment: Always Neutral
Advancement: 7-12 HD (Large)
Level Adjustment: ---

"I don't care what it is. I don't care if it chews up the whole state. I care if it came from Mars or happened by spontaneous combustion. We're going to Canada with a load of gold, so forget it!"

The Beast from Haunted Cave appears to have potentially hatched from an egg (which the film implies was recently), and there are no signs of there being more of it's kind. This also implies it may be an infant, and adults may be significantly larger and more powerful. It was apparently fairly tough, and while gunfire drove it off, it didn't appear to permanently injure it until the end of the film, when mass gunfire (and a liberal dose of flame) puts an end to it. The beast appears vaguely humanoid, but spend much of it's time crouched on all fours walking in a spiderlike gait. It's front limbs are incredibly long tentacles, and most of it's other features are obscured by long hair (which may be hair or some sort of filament similar to it's webbing).

The Beast lives in an abandoned mine near Deadwood, South Dakota, where it is discovered by a group of bank robbers on the run. In fact, the explosives they set in the mine to serve as a distraction may have hatched the Beast or driven it from the mine.

Improved Grab (Ex): If the Beast successfully hits with it's Tentacle Attack, it may immediately make a Grapple Check as a Free Action without provoking an Attack of opportunity. If successful it may Grapple it's victim, cocoon it, or drink it's blood.

Blood Drain (Ex): If the Beast has it's opponent pinned in a Grapple, or it has it cocooned and helpless, it may do 1d4 temporary Strength damage per round.

Webbing (Ex): The Beast may cocoon unconscious, paralyzed or helpless victims with some sort of weblike substance. Once they awake they can try to escape from the cocoon, but with their arms and legs bound as they are they will have to make a successful DC 18 Escape Artist Check or DC 22 Strength Check to break free. The Save DC is Constitution based, and the Strength Check DC has a +4 Racial Bonus. The Beast can cocoon a Tiny or Smaller opponent as a Standard Action, and a Small or Medium opponent as a Full Round Action. It will not willingly attack opponents larger than itself, but could, in theory, cocoon them as well.

Frightful Presence (Ex): When the Beast Grapples or Charges an opponent, all enemies with less than 6 HD within 30 ft. must make a DC 16 Willpower Save (Save DC is Charisma based) or be Shaken for the duration of the encounter.

Snow Walk (Ex): The Beasts movement is not slowed by snow and ice.

Skills: The Beast gains a +4 Racial Bonus to Climb and Hide Checks.

Combat: The Beast normally does non lethal damage with it's tentacle attacks (it takes no attack roll penalty when it does this) and Grapple Checks because it wants live victims. Once it has grappled them into unconsciousness it takes them to it's lair or other convenient hiding place and cocoons them in webbing so it can use their blood as a food source. Since it does not feed them they eventually die of a combination of blood loss and starvation.