Spider Eater (CR 5)

Large Magical Beast
Alignment: Always neutral
Initiative: +1 (Dex); Senses: darkvision 60 ft., low-light vision, scent, Listen +10, and Spot +11

AC: 14 (-1 size, +1 Dex, +4 natural), touch 10, flat-footed 13
Hit Dice: 4d10+20 (42 hp)
Fort +9, Ref +5, Will +2
Speed: 30 ft., fly 60 ft. (good)
Space: 10 ft./5 ft.
Base Attack +4; Grapple +13
Attack: Sting +8 melee
Full Attack: Sting +8 melee and bite +3 melee
Damage: Sting 1d8+5 and poison, bite 1d8+2
Special Attacks/Actions: Poison, implant
Abilities: Str 21, Dex 13, Con 21, Int 2, Wis 12, Cha 10
Special Qualities: Freedom of movement
Feats: Alertness; Dodge
Skills: Listen +10 and Spot +11
Advancement: 5-12 HD (Huge)
Climate/Terrain: Temperate forest
Organization: Solitary
Treasure/Possessions: None

Source: Monster Manual

Poison (Ex): Bite, Fortitude save (DC 17); initial damage none, secondary damage paralysis for 1d8+5 weeks.

Implant (Ex): Female spider eaters lay their eggs inside paralyzed creatures of Huge or larger size. The young emerge about six weeks later, literally devouring the host from inside.

Freedom of Movement (Su): Spider eaters have freedom of movement as though from the spell cast by a 12th-level sorcerer. The effect can be dispelled, but the spider eater can create it again the next round as a free action. When the spider eater serves as a mount, this effect does not extend to its rider.

Skills: Spider eaters receive a +4 racial bonus to Listen and Spot checks.

A spider eater attacks with its venomous sting and powerful mandibles. Its usual tactic is to deliver a sting, then back off, hovering out of reach until the venom takes effect. Spider eaters do not like to give up their prey, and foes who harry them with spells or ranged attacks provoke a determined counterattack.