Mnemonicus (CR 3 o)

Tiny Aberration (Symbiont)
Alignment: Usually lawful evil
Initiative: +2 (Dex); Senses: blindsight 60 ft. and darkvision 60 ft.
Languages: Common, Draconic, Infernal, and Undercommon

AC: 16 (+2 size, +2 Dex, +2 natural), touch 14, flat-footed 14
Hit Dice: 1d8 (4 hp)
Fort +0, Ref +2, Will +4
Speed: 5 ft.
Space: 2 1/2 ft./0 ft.
Base Attack +0; Grapple -13
Attack: Slam +4 melee
Full Attack: Slam +4 melee
Damage: Slam 1d2-5
Special Attacks/Actions: Brain consumption, invade, spells
Abilities: Str 1, Dex 14, Con 11, Int 18, Wis 15, Cha 16 (Ego: 19)
Special Qualities: recall, symbiont traits
Feats: Silent Spell; Weapon Finesse
Skills: Concentration +4 Hide +14, Knowledge (arcana) +8, Knowledge (religion) +8, Knowledge (the planes) +8, and Spellcraft +8
Advancement: -
Climate/Terrain: Any underground
Organization: Solitary (symbiont)
Treasure/Possessions: -

Source: Dragon #308

Blindsight (Ex): A mnemonicus is blind, but its entire body is a primitive sensory organ that can ascertain objects and creatures by scent and vibration within 60 feet. A mnemonicus usually does not need to make Spot or Listen checks to notice creatures within range of its blindsight.

Brain Consumption (Ex): When the mnemonicus first embeds its tentacles in a host creature's brain, it ingests some of the host's brain. The host must make a successful Will save (DC 13) or take 1d6 points of permanent Intelligence drain and behave as though under the influence of a confusion spell (caster level 7th) for 1 hour. (The host may waive the saving throw to gain the benefits of symbiosis with the creature if desired.) The drained Intelligence cannot be replaced by any means as long as the mnemonicus is in residence. However, the creature then replaces the lost Intelligence with some of its own, resulting in no net loss to the host. The mnemonicus can be slain after taking up residence only with a heal spell. Should the mnemonicus die or otherwise detach from the host, however, the replacement Intelligence is gone and the host again takes the effects of the initial loss.

Improved Grab (Ex): If a mnemonicus hits an opponent of any size, with a slam attack, it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity (grapple bonus +7). If it gets a hold, it can attempt to invade the target creature (see below).

Invade (Ex): If a mnemonicus successfully grapples a foe, it can use a subsequent grapple check (usually during its action on the following round) to try to embed its tentacles deep in its opponent's brain. The mnemonicus and the grappled opponent make opposed grapple checks. If the mnemonicus succeeds, it can immediately use its brain consumption special attack.

Spells: A mnemonicus can cast spells as a 3rd-level sorcerer.

Typical Spells Known (6/6; save DC 13 + spell level): 0 - acid splash, detect magic, ray of frost, read magic, resistance; 1st - expeditious retreat, magic missile, shield.

Recall (Su): The mnemonicus allows the host to instantly recall up to nine levels of spells already cast or regain 18 psionic power points already used. The host can recall any desired spells cast so long as their spell levels add up to nine or less. These spells need not all be recalled at once. For example, a wizard host who had prepared one fireball spell for the day could recall and recast that spell three times in succession, or she could recall fireball once, dispel magic once, and sleep three times, or she could recall meteor swarm once. Each day that the recall ability is used, the host takes 2 points of Intelligence damage, regardless of how many spell levels are recalled or power points regained.

A mnemonicus attacks by leaping up to slam the potential host's head, wriggling its tentacles through any available orifice (ear, nose, mouth, or the like), and then attaching itself to the back of its host's head. It consumes enough of the host's brain matter to give its tentacles room for firm purchase.