Greenvise (CR 10)

Huge Plant
Alignment: Always neutral
Initiative: +0; Senses: woodsense

AC: 16 (-2 size, +8 natural), touch 8, flat-footed 16
Hit Dice: 12d8+48 (102 hp)
Fort +12, Ref +4, Will +4
Speed: 10 ft.
Space: 15 ft./15 ft.
Base Attack +9; Grapple +26
Attack: Slam +16 melee
Full Attack: 4 slams +16 melee and bite +11 melee
Damage: Slam 2d4+9, bite 1d6+4
Special Attacks/Actions: Death fog, improved grab, swallow whole
Abilities: Str 29, Dex 10, Con 18, Int 3, Wis 11, Cha 6
Special Qualities: Acid immunity, plant traits
Feats: Cleave; Improved Initiative; Improved Critical (bite); Power Attack; Skill Focus (hide)
Skills: Hide +10
Advancement: 13-18 HD (Huge); 19-36 HD (Gargantuan)
Climate/Terrain: Temperate or warm hills, plains or marsh
Organization: Solitary, pair, or patch (3-8)
Treasure: None

Source: Monster Manual II

Greenvises are ambulatory vegetable horrors that stalk the fringes of some humanoid settlements. These carnivorous plants are not bold - they prefer to ambush lone prey that happens to come too near. Greenvises rest at night and actively hunt during daylight hours, repositioning themselves throughout the day if prey in a particular hunting area proves scarce.

A greenvise is a larger, sturdier version of the venus fly-trap, with a thick, green, trunk-like stem and four sturdy tendrils that hang down like vines. When the creature opens its mouth, a mottled pink maw lined with tooth-like thorns is revealed; when closed, the mouth structure resembles an ordinary leafy bush. A greenvise has small tendril-like roots that it uses to move.