Soul Tick (CR 1/8)

Fine Outsider (Evil, Extraplanar, lawful, and Symbiont)
Alignment: Always lawful evil
Initiative: +3 (Dex); Senses: darkvision 60 ft. and Spot +4
Languages: Telepathy with host


AC: 21 (+8 size, +3 Dex), touch 21, flat-footed 18
Hit Dice: 1/4d8 (1 hp)
Fort +2, Ref +5, Will +2
Speed: 5 ft.
Space: 1/2 ft./0 ft.
Base Attack +1; Grapple -20
Attack: Bite +12 melee
Full Attack: Bite +12 melee
Damage: Bite attach
Special Attacks: Attach, blood drain
Abilities: Str 1, Dex 16, Con 11, Int 14, Wis 11, Cha 8 (Ego: 13)
Special Qualities: enhance magic, impede magic, protective aura, outsider traits, symbiont traits, vulnerable to holy power
Feats: Weapon Finesse
Skills: Concentration +4, Diplomacy +3, Hide +23, Knowledge (any two) +6 Listen +4, Move Silently +7, Spot +4, and Survival +4
Advancement: -
Climate/Terrain: Any land and underground (Nine Hells)
Organization: Solitary (symbiont)
Treasure/Possessions: -

Source: Fiend Folio

The soul rick is an infernal arachnid that attaches itself to a host's skin and feeds on its blood. Its body is about 1 inch in diameter, swelling to 2 inches when full of blood (or up to about 4 inches when it overfeeds). It is covered with a thin chitinous shell of a dark reddish-brown color, shading to bright red at the ends of its legs and its complex mouth. When attached to its host, its legs and head burrow into the host's flesh, leaving just its body visible.

Soul ticks do not speak, but they understand Infernal.

Combat

Unlike other fiendish symbionts soul ticks can make melee attacks. The creatures preferred method of attack, however, is to hide in whatever terrain is available and attack creatures that pass through its space, using surprise to avoid attacks of opportunity. Once attached, it uses telepathy to communicate with its new host, trying to persuade it not to remove the tick and explaining its powers.

Attach (Ex): if a soul tick hits with its bite attack, it uses its mouth and eight legs to burrow into the target's flesh, latching firmly onto the opponents body. An attached soul tick loses its Dexterity bonus to AC, making its AC 18.

Blood Drain (Ex): A soul tick drains blood, dealing 1 point of Constitution damage each day it remains attached. Ordinarily, the host regains 1 lost Constitution point each night, just before the soul tick drains 1 new point, keeping the host at an equilibrium point of -1 to its normal Constitution. However, once per day as a full-round action the soul tick can overfeed, draining enough blood to deal 1d4 points of Constitution damage to its host, usually as punishment for displeasing it.

Enhance Magic (Ex): Any spells with the death or evil descriptor, as well as spells that use negative energy in any way, are enhanced when cast by the soul tick's host. Such spells are automatically empowered without changing the spell slot required or casting time.

Impede Magic (Ex): Any spells with the chaos or good descriptor, as well as spells that use positive energy in any way, are impeded when cast by the soul tick's host. The host must make a Spellcraft check (DC 15 + spell level) when trying to cast such a spell, if this check fails, the spell does not function and is lost. If the check succeeds, the spell functions normally.

Protective Aura (Su): A protection from good or protection from chaos effect constantly wards a soul tick and its host, as the appropriate spell cast by a 12th-level sorcerer. The soul tick can change the aura at will as a free action. The aura can be dispelled, but the soul tick can create it again during its next turn as a free action. (The defensive benefits from the aura are not included in the creature's statistics.)

Vulnerable to Holy Power (Ex): A soul tick's host is affected by holy power (such as holy smite spells and weapons with the holy property) as if the creature were evil, regardless of its actual alignment.

Outsider Traits: A fiendish symbiont has darkvision (60-foot range). It cannot be raised or resurrected (though a wish or miracle spell can restore life).

Telepathy (Su): A fiendish symbiont can communicate telepathically with its host creature, if the host has a language.

Symbiont Traits: When joined with a host, a symbiont gains a number of benefits. It acts on its host's turn each round, regardless of its own initiative modifier. It is not flat-footed unless its host is, and it is aware of any danger its host is aware of.

If a symbiont is grafted onto a visible part of the host creature's body, opponents can attack the symbiont itself instead of its host creature. This works the same way as attacking an object: The symbiont gains the benefit of the host's Dexterity modifier to AC instead of its own, and gains any deflection bonus to AC the host has as well. Its own size modifier and natural armor bonus, if any, apply. Attacking a symbiont instead of its host provokes an attack of opportunity from the host.

A symbiont never takes damage from attacks directed at the host. Like a worn magic item, a symbiont is usually unaffected by spells that damage the host, but if the host rolls a 1 on its saving throw, the symbiont is one of the "items" that can be affected by the spell. A symbiont uses its host's base saving throw bonuses if they are better than its own.

Share Spells (Su): Any spell the host creature casts on itself automatically also affects the symbiont. Additionally, the host may cast a spell with a target of "Self" on the symbiont instead of on itself. Likewise, a symbiont can choose to have any spell or spell-like ability it uses on itself also affect the host creature, and may cast a spell with a target of "Self" on its host instead of on itself. The host and symbiont can share spells even if the spells normally do not affect creatures of the host or symbiont's type. Spells targeted on the host by another spellcaster do not affect the symbiont, and vice versa.