Brood Mother (CR 14)

Large Aberration
Alignment: Always chaotic evil
Initiative: +7 (+3 Dex, +4 Improved Initiative); Senses: Listen +10 and Spot +10

AC: 21 (+3 Dex, -1 size, +9 natural), touch 9, flat-footed 18
Hit Dice: 18d8+90 (171 hp)
Fort +11, Ref +9, Will +14
Speed: 40 ft., 30 ft. climb
Space: 20 ft./10 ft.
Base Attack +13; Grapple +13
Attack: Bite +14 melee
Full Attack: Bite +14 melee
Damage: Bite 4d6+12 and poison
Special Attacks/Actions: Poison, spell-like abilities, web
Abilities: Str 27, Dex 17, Con 20, Int 6, Wis 16, Cha 16
Special Qualities: Immunities, SR 25
Feats: Alertness; Combat Casting; Improved Initiative
Skills: Climb +17, Concentration +10, Listen +10, and Spot +10
Advancement: 19-36 HD (Gargantuan); 37-54 (Colossal)
Climate/Terrain: Underground
Organization: Solitary or brood (1 brood mother, 10-20 Small monstrous spiders, 1-10 Large monstrous spiders, 1-6 Huge monstrous spiders)
Treasure/Possessions: Standard

Source: Dragon #298

Immunities (Ex): Brood mothers are immune to webs (they cannot be caught in a spider's web or a web spell), poisons, and mind-affecting effects.

The poison injected by a brood mother is actually a tiny egg in a fluid that causes rapid growth of the egg under the right conditions. The bodies of creatures killed by a brood mother's poison burst apart as a monstrous spider, already grown to maturity, is born to the world. The birthed spider's size is always one size category smaller than the creature that gave it birth. Thus, an ogre killed by a brood mother's poison would give birth to a Medium-size monstrous spider. When a creature succeeds at the second saving throw against the brood mother's poison, its body has nullified the growth liquid and killed the egg.

Spell-like Abilities: 3/day - dancing lights, darkness, deeper darkness, detect chaos, detect evil, detect good, detect law, detect magic, faerie fire. Caster level 14th; save DC 13 + spell level.

Web (Ex): Brood mothers spin webs as monstrous spiders. They may cast a web eight times per day. This is similar to an attack with a net, but has a maximum range of 50 feet with a range increment of 10 feet and is effective against targets of Huge or smaller size (see Net for details on net attacks). The web anchors the target in place, allowing no movement.

An entangled creature can escape with a successful Escape Artist check (DC 30) or burst it with a Strength check (DC 36). Both are standard actions. The web has 16 hit points. See monstrous spider for more information about webs.

Brood mothers prefer to fight from behind a shield of their monstrous spider kin.