Sewerm (CR 2)

Small Animal
Alignment: Always neutral
Initiative: +3 (Dex); Senses: low-light vision, scent, Listen +7, and Spot +7

AC: 17 (+1 size, +3 Dex, +3 natural), touch 14, flat-footed 14
Hit Dice: 2d8 (9 hp)
Fort +3, Ref +6, Will +1
Speed: 20 ft., climb 20 ft., swim 20 ft.
Space: 5 ft./5 ft.
Base Attack +1; Grapple +16
Attack: Bite +5 melee
Full Attack: Bite +5 melee
Damage: Bite 1d4+4
Special Attacks/Actions: Attach, blood drain, poison
Abilities: Str 17, Dex 17, Con 11, Int 2, Wis 12, Cha 2
Special Qualities:
Feats: Alertness; Weapon Finesse
Skills: Balance +11, Climb +11, Hide +18, Jump +7, Listen +7, Spot +7, and Swim +11
Advancement: 3-4 HD (Medium); 5-6 HD (Large)
Climate/Terrain: Temperate marshes
Organization: Solitary
Treasure/Possessions: None

Source: Serpent Kingdoms

Attach (Ex): If a sewerm hits with a bite attack, it latches onto the opponent's body and is effectively grappling its prey. The sewerm loses hs Dexterity bonus to AC and has an AC of 14. A sewerm has a +16 racial bonus on grapple checks (already figured into the Base Attack/Grapple entry above).

An attached sewerm can be struck with a weapon or grappled itself. To remove an attached sewerm through grappling, the opponent must achieve a pin against it.

Blood Drain (Ex): A sewerm drains blood, dealing automatic bite damage in any round when it begins its turn attached to a victim. Once it has dealt 30 points of damage, it detaches and flees to digest the meal.

Poison (Ex): A sewerm's "venom" is actually an anesthetic oil secreted through its skin and fangs. This oil prevents its target from feeling pain at the point of contact, even if it is taking hit point damage. The sewerm uses this oil to prevent its victims from noticing its presence while it feeds. Bite, injury or contact, Fortitude DC 11; initial and secondary damage anesthetic. The save DC is Constitution-based.

Skills: A snake has a +4 racial bonus on Hide, Listen, and Spot cheeks and a +8 racial bonus on Balance and Climb checks. A snake can always choose to take 10 on a Climb check, even if rushed or threatened. A snake uses either its Strength modifier or its Dexterity modifier for Climb checks, whichever is higher.

A sewerm has +8 racial bonus on Jump checks, and its racial bonus on Hide checks is +8 instead of +4. It also has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Unless threatened, sewerms attack only warm-blooded creatures. A sewerm typically attaches to a victim's limb (preferably one that extends underwater) with a bite attack, then wraps its body around the limb. Once so secured, it begins draining blood. Because of the anesthetic secretions a sewerm secretes from its fangs and skin, most victims are unaware of its presence. The creature can also coil itself up and spring out of the water to strike a target that cannot be attacked below the water (such as a humanoid wearing hip boots).