Saguaro Sentinel (CR 9)

Huge Plant
Alignment: Usually neutral
Initiative: -1 (Dex); Senses: low-light vision, Listen +3, and Spot +8
Languages: Sylvan, those of above average intelligence also know the Treant language.

AC: 22 (-2 size, -1 Dex, +15 natural), touch 7, flat-footed 22
Hit Dice: 12d8+84 (138 hp); DR: 10/piercing
Fort +15, Ref +3, Will +5
Speed: 20 ft.
Space: 15 ft./15 ft.
Base Attack +9; Grapple +28
Attack: Slam +18 melee (3d6+11) or
2 slams +18 melee (3d6+11)
Special Attacks/Actions: Thorns, trample 3d6+16
Abilities: Str 33, Dex 8, Con 25, Int 10, Wis 13, Cha 14
Special Qualities: plant traits, tough flesh
Feats: Alertness; Awesome Blow; Improved Bull Rush; Improved Natural Attack; Power Attack
Skills: Disguise +2*, Intimidate +12, Knowledge (nature) +10, Listen +3, Spot +8, and Survival +6 (+8 aboveground)
Advancement: 13-16 HD (Huge); 17-36 HD (Gargantuan)
Climate/Terrain: Warm deserts
Organization: Solitary or stand (2-5)
Treasure/Possessions: Standard

Source: Sandstorm

Thorns (Ex): The body of a saguaro sentinel is covered with long, cruel thorns. These thorns tear at any creature that touches it, dealing 1d6 points of piercing damage. Creatures striking a saguaro sentinel with natural attacks or unarmed strikes are subject to this damage, but creatures striking with melee weapons are not. A creature that is pushed into or falls onto a plant also takes damage from its thorns.

Trample (Ex): Reflex DC 27 half. The save DC is Strength-based.

Tough Flesh (Ex): The flesh of a saguaro sentinel is tough and retains water in the harshest of conditions. It does not take extra damage from dehydration spells and effects (including horrid wilting) as plants normally do.

Skills: *A saguaro sentinel has a +12 racial bonus on Disguise checks to resemble an inanimate plant.

A saguaro sentinel spends most of its time standing and watching. It prefers higher ground, as long as it has soil in which to root, so it can observe larger portions of the waste. If interlopers are causing harm to desert life, a sentinel barrels down on them without warning.