Triceratops, Cave (CR 5)

Large Animal
Alignment: Always neutral
Initiative: -1 (Dex); Senses: darkvision 60 ft., scent, Listen +9, and Spot +8

AC: 18 (-1 size, -1 Dex, +10 natural), touch 8, flat-footed 18
Hit Dice: 8d8+40 (76 hp)
Fort +13, Ref +5, Will +3
Speed: 30 ft.
Space: 10 ft./10 ft.
Base Attack +6; Grapple +14
Attack: Gore +10 melee
Full Attack: Gore +10 melee
Damage: Gore 2d6+6
Special Attacks/Actions: Powerful charge, trample 3d6+6
Abilities: Str 19, Dex 8, Con 21, Int 1, Wis 12, Cha 6
Special Qualities:
Feats: Alertness; Great Fortitude; Weapon Focus (gore)
Skills: Listen +9 and Spot +8
Advancement: 9-12 HD (Large); 13-24 HD (Huge)
Climate/Terrain: Underground
Organization: Solitary or brood (2-8 plus 50% chance for 1 leader with 12 HD)
Treasure/Possessions: None

Source: Miniatures Handbook

Powerful Charge (Ex): When a cave triceratops charges, its gore attack deals 4d6+12 points of damage.

Trample (Ex): Reflex DC 18 half. The save DC is Strength-based.

A cave triceratops doesn't fear combat, or much of anything. Unless it's badly wounded, it prefers to trample creatures that disturb it underfoot.