This tiny creature appears to be a gray-green leech.
Wizard’s Shackle CR 1/3
Speed 5 ft.
Melee bite +5 (1d2-5 plus attach)
Space 1 ft.; Reach 0 ft.
Special Attacks spell drain
A wizard’s shackle attacks from ambush. It favors hiding on ledges, bookshelves, doors, and other such places where it can drop on spellcasters that pass underneath it. A wizard’s shackle injects an anesthetic when it bites, so it is possible that its bite goes unnoticed (DC 12 Perception check to notice).
A wizard’s shackle can automatically detect the location of any arcane spellcaster within 30 feet.
If a wizard’s shackle hits with a bite attack, it latches onto the opponent’s body. An attached wizard’s shackle is effectively grappling its prey. The wizard’s shackle loses its Dexterity bonus to AC and has an AC of 14, but holds on with great tenacity. Wizard’s shackles have a +20 racial bonus on grapple checks (already figured into the CMB and CMD entries above).
A wizard’s shackle is immune to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
A wizard’s shackle drains spells when attached to an arcane spellcaster. Each round the wizard’s shackle remains attached, it drains 1d6 levels of prepared spells or unused slots, beginning with the highest level spell or slot available. For example, on a roll of 4 against a 5th-level wizard, a wizard’s shackle drains four levels of prepared spells. The wizard currently has one 3rd-level spell, two 2nd-level spells, and three 1st-level spells prepared. The wizard’s shackle drains the 3rd-level spell and one of the 1st-level spells (determined randomly).
A creature drained of spells or slots can attempt a DC 12 Intelligence check with a +2 bonus to notice that something is wrong (though unless he searches his body, he might still overlook the wizard’s shackle). Once a wizard’s shackle has drained at least 4 spell levels, it detaches and crawls away to digest its meal. Lost spells or slots can be regained normally.
Organization colony (2-5), swarm (6-11)
The wizard’s shackle is a 6-inch long, leech-like creature. Though it is small in size, it is greatly feared by spellcasters, for its bite drains arcane magic from a caster’s mind. In some rare instances, evil spellcasters have harvested these monsters and set them loose in an enemy spellcaster’s tower or laboratory.
Wizard’s Shackle from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene.