Vile Water Roots (CR 8)

Huge Plant
Alignment: Always neutral evil
Initiative: -1 (Dex); Senses: blood scent, tremorsense, Listen +13, and Spot +13

AC: 20 (-2 size, -1 Dex, +13 natural), touch 7, flat-footed 20
Hit Dice: 13d8+65 (123 hp); DR: 10/good
Fort +13, Ref +5, Will +4
Speed: Swim 30 ft., burrow 30 ft.
Space: 10 ft./10 ft.
Base Attack +9; Grapple +13
Attack: Bite +17 melee
Full Attack: Bite +17 melee
Damage: Bite 2d6+13 and 2d6 unholy/19-20
Special Attacks/Actions: Improved grab, swallow whole, smite good
Abilities: Str 28, Dex 9, Con 21, Int 7, Wis 11, Cha 10
Special Qualities: Blood scent, magic circle against good, plant traits, SR 19, unholy bite
Feats: Improved Critical (bite); Lightning Reflexes; Weapon Focus (bite)
Skills: Hide +4, Listen +13, and Spot +13
Advancement: 14-16 HD (Huge); 17-32 HD (Gargantuan); 32-48 HD (Colossal)
Climate/Terrain: Any land
Organization: Solitary
Treasure/Possessions: None

Source: Web

Improved Grab (Ex): If the vile water roots hits an opponent that is at least one size category smaller than itself with a bite attack, it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity (grapple bonus +26). If it gets a hold, it can attempt to swallow on the next round (see below). Alternatively, the root has the option to conduct the grapple normally, or simply use its jaws to hold the opponent (-20 penalty on the grapple check, but the root is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals bite damage.

Smite Good (Su): Once per day, a vile water roots can make a normal attack to deal +13 points of damage to a good foe.

Swallow Whole (Ex): A vile water roots can swallow a grabbed creature that is at least one size category smaller than itself by making a successful grapple check (grapple bonus +26), provided it already has that opponent in its maw (see Improved Grab, above). Once inside the root, the opponent takes 2d6+13 points of bludgeoning damage and 1d4 points of Constitution damage from blood drain per round from hundreds of tiny, biting and sucking mouths inside the vile water roots. A successful grapple check allows the swallowed creature to climb out of the interior and return to the root's maw, where another successful grapple check is needed to get free. Alternatively, a swallowed creature can try to cut its way out with either claws or a light piercing or slashing weapon. Dealing at least 25 points of damage to the interior (AC 20) in this way creates an opening large enough to permit escape. Once a single swallowed creature exits, the hole seals; thus, another swallowed opponent must cut its own way out. The root's interior can hold 1 Large, 2 Small, 4 Tiny, 8 Diminutive, or 16 Fine opponents.

Blood Scent (Su): A vile water roots can sense the presence of all animals, beasts, dragons, fey, giants, humanoids, magical beasts, monstrous humanoids, outsiders, and shapechangers within 60 feet. (Constructs, elementals, oozes, plants, undead, and vermin are not noticed by this supernatural ability.)

Magic Circle against Good (Su): This ability continuously duplicates the effects of the spell of the same name. The vile water roots cannot suppress this ability.

Tremorsense (Ex): Roots of all evil can automatically sense the location of anything within 60 feet that is in contact with the ground.

Unholy Bite (Ex): A vile water roots' bite attack functions as an unholy weapon and deals +2d6 points of bonus unholy (evil) damage against all of good alignment.

Feats: A vile water roots gains feats as though it were an undead.

Skills: A vile water roots receives skill as though it were undead. It has a +20 racial bonus on Hide checks in areas with other vegetation.

An aquatic plant counterpart to the roots of all evil, the vile water root inhabits sizeable bodies of salt water. It usually chooses to dwell near sunken ships, especially those inhabited by undead. Vile water roots hate life and seek to kill all living, blood-bearing beings that they encounter. Odd in appearance, a vile water roots resembles a large parsnip with a vicious maw surrounded by green, ferny foliage like the top. A vile water roots feeds primarily on blood, but also needs at least two hours of sunlight per week.

Vile water roots are never found with others of their kind. However, undead often form a happenstance symbiotic partnership with the plant by inhabiting areas frequented by a vile water roots. They benefit from the root's magic circle against good and the root benefits from the undead's occasional flanking and additional attacks, especially when attacking a group of living creatures.

Vile water roots generally rest underground, waiting for the vibrations that indicate a creature passing nearby. If their blood scent perceives a likely foe, roots burrow to the surface, seeking to surprise their prey, grabbing it and swallowing it whole.