Shambling Mound (CR 6)

Large Plant
Alignment: Always neutral
Initiative: +0; Senses: darkvision 60 ft. and Listen +8

AC: 20 (-1 size, +11 natural), touch 9, flat-footed 20
Hit Dice: 8d8+24 (60 hp)
Fort +9, Ref +2, Will +4
Speed: 20 ft.
Space: 10 ft./10 ft.
Base Attack +6; Grapple +15
Attack: Slam +11 melee
Full Attack: 2 slams +11 melee
Damage: Slam 2d6+7
Special Attacks/Actions: Improved grab, constrict 2d6+7
Abilities: Str 21, Dex 10, Con 17, Int 7, Wis 10, Cha 9
Special Qualities: electricity immunity, Plant, fire resistance 10
Feats: Iron Will; Power Attack; Weapon Focus (slam)
Skills: Hide +3*, Listen +8, and Move Silently +8
Advancement: 9-12 HD (Large); 13-24 HD (Huge)
Climate/Terrain: Temperate marsh
Organization: Solitary
Treasure/Possessions: 1/10th coins; 50% goods; 50% items

Source: Monster Manual

Improved Grab (Ex): To use this ability, the shambler must hit an opponent of up to Large size with both arm attacks. If it gets a hold, it can constrict.

Constrict (Ex): A shambler deals 2d6+7 points of damage with a successful grapple check against Large or smaller creatures. The shambler can still move but cannot take any attack actions when constricting.

Electricity Immunity (Ex): Shamblers take no damage from electricity. Instead, any electrical attack (such as shocking grasp or lightning bolt) used against a shambler grants it 1d4 points of temporary Constitution. The shambler loses these points at the rate of 1 per hour.

Skills: Shamblers receive a +4 racial bonus to Hide, Listen, and Move Silently checks. They receive a +12 bonus to Hide checks when in a swampy or forested area.

A shambling mound batters or constricts its opponents with two huge, arm-like appendages.