Century Worm (CR 19)

Gargantuan Vermin
Alignment: Always neutral
Initiative: -2 (Dex); Senses: tremorsense 120 ft.

AC: 29 (-4 size, -2 Dex, +25 natural), touch 4, flat-footed 29
Hit Dice: 40d8+240 (420 hp)
Fort +28, Ref +11, Will +13
Speed: 30 ft., burrow 20 ft., swim 10 ft.
Space: 20 ft. (coiled)/15 ft.
Base Attack +30; Grapple +54
Attack: Bite +38 melee
Full Attack: Bite +38 melee
Damage: Bite 4d6+18
Special Attacks/Actions: Improved grab, keening, swallow whole, wriggling progeny
Abilities: Str 35, Dex 7, Con 22, Int -, Wis 11, Cha 2
Special Qualities: Acid resistance 20, vermin traits
Feats: -
Skills: Swim +20
Advancement: 41-80 HD (Gargantuan); 81-120 HD (Colossal)
Climate/Terrain: Any land and underground
Organization: Solitary
Treasure/Possessions: -

Source: Fiend Folio

Improved Grab (Ex): If a century worm 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 +54). If it gets a hold, it automatically deals bite damage and can attempt to swallow the foe. Thereafter, the century worm has the option to conduct the grapple normally, or simply use its bite to hold the opponent (-20 penalty on grapple check, but the century worm is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals bite damage.

Keening (Ex): Once per round as a free action, a century worm can emit a terrible keening sound. All living creatures within 50 feet of the worm must make successful Fortitude saves (DC 38) to avoid being deafened by the sound.

Swallow Whole (Ex): A century worm can swallow a single creature that is at least one size category smaller than itself by making a successful grapple check (grapple bonus +54), provided it already has that opponent in its maw (see Improved Grab, above). Once inside the century worm, the opponent takes 2d6+9 points of acid damage per round from the worm's stomach. A successful grapple check allows the swallowed creature to climb out of the stomach and return to the century worms maw where another successful grapple check 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 a total of at least 40 points of damage to the stomach (AC 22) in this way creates an opening large enough so permit escape. Once a single swallowed creature exits, muscular action closes the hole; thus, another swallowed opponent must cut its own way out. A century worm's maw can hold 2 Large, 8 Medium size, 32 Small, or 128 Tiny as smaller opponents.

Wriggling Progeny (Ex): Characters trapped within a century worm's stomach must make a successful Fortitude save (DC 38) every round or take 1d8 points of Constitution damage as century worm larvae burrow through the victim's skin and make their way toward its heart.

A successful save staves off Constitution damage for that round only.

When a victim's Constitution reaches 0, the victim dies and a single century worm larva digs into its flesh and attaches itself to the corpse's spine. The larva can be destroyed by a remove disease spell. If it is not destroyed, a new century worm begins to grow inside the body. This larval form begins as a Tiny creature with 20 hit points and grows one size category every 20 years (gaining another 80 hit points for every size change). When its size is the same as the size of its host body, the worm bursts forth from within the body. It continues to feed on the remains of the body until, after 100 years, it reaches Gargantuan size and becomes a fully formed century worm.

Bodies currently serving as incubators for century worm-larvae cannot be returned to life by any means.

Tremorsense (Ex): A century worm can automatically sense the location of anything within 120 feet that is in contact with the ground.

Vermin Traits: A century worm is immune to all mind-affecting effects (charms, compulsions, phantasms, patterns and morale effects). It also has darkvision (60-foot range).

Skills: A century worm has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard and can always choose to take 10 on Swim checks, even if distracted or endangered.

From the moment of its birth, a century worm exists only to destroy. It mindlessly attempts to swallow any living creature it encounters by lunging in with a forceful attack and finishing off enemies with a satisfying gulp.

Some believe that nature is a chaotic, destructive force that cares little for the concepts of morality or fair play. Such devotees of wild destruction and entropy often point to the dreaded century worm as evidence of their philosophy and single out the repulsive, voracious creature as the living embodiment of the uncaring wrath of the natural world.

A century worm is composed of seven translucent segments of pulpy flesh topped by a menacing head partially covered by a hood of rough, dark brown skin. Its round, tooth-lined mouth easily accommodates an ogre. Hundreds of squirming larvae about the size of a human's arm line the worm's stomach, which doubles as a womb. These little creatures sometimes spill out of the worm's mouth, though they die within an hour for want of their parent's life-giving nutrient bile.

Century worm larvae are far from harmless to creatures that find themselves trapped within the parent. Once the litter has sapped the life out of a victim, one larva takes up residence in the victim's body, where it gestates for a period of 100 years.