Leechwalker (CR 10)

Medium Vermin
Alignment: Always neutral
Initiative: +0; Senses: all-around vision, Listen +5, and Spot +8

AC: 12 (+2 natural), touch 10, flat-footed 12
Hit Dice: 13d8+39 (97 hp); DR: 10/piercing or slashing
Fort +11, Ref +4, Will +5
Speed: 30 ft., swim 20 ft.
Space: 5 ft./5 ft.
Base Attack +9; Grapple +13
Attack: 2 tentacle rakes +13 melee
Full Attack: 2 tentacle rakes +13 melee
Damage: Tentacle rake 1d8+4 plus wounding
Special Attacks/Actions: Blood drink, improved grab, wounding
Abilities: Str 18, Dex 11, Con 16, Int -, Wis 13, Cha 7
Special Qualities: immunities, vermin traits
Feats: -
Skills: Hide +3, Listen +5, Move Silently +5, Search +4, Spot +8, and Swim +12
Advancement: 14-26 HD (Medium-size); 27-39 HD (Large)
Climate/Terrain: Any marsh or underground
Organization: Solitary, pair, or gang (3-5)
Treasure: None

Source: Monster Manual II

The leechwalker is a thirsty vermin that can drain a creature of all its blood in a matter of moments. It usually lurks in swamps or damp underground areas.

A leechwalker appears to he a massive, 6-foot-tall humanoid covered with thousands of dark, writhing leeches. Though it has a head, it possesses no recognizable facial features. Its body is slick, as if coated with a thin layer of clear slime, and it has an impossibly bloated stomach.