Magebane

Found in tombs, ruins and caves, a magebane looks like a large black bat with cold, glowing blue eyes and a thin barbed tail, its formless underside bristling with at least ten long, spindly black claws. It feeds on magic by attaching itself to a strong spellcaster, its chosen one, and soon becomes a serious burden.

Normally only the chosen one can see it. Psionics neither detect nor affect it, and it cannot sense them in turn, but it sees magical auras and can tap spells cast as far as 160 feet off. Silent and careful to stay out of its host's view, since the host is best placed to spot and kill it, it can go unnoticed for a long while.

Hovering near its host, usually behind, the magebane feeds on 60% of the spells the host casts. Roll 1d6: on 1-2 the spell is consumed and fizzles, much as with a rod of absorption; on 3-6 it is weakened, taking minimum duration, minimum damage, a reduced area or volume, or giving targets +2 or more on saves (one or more of these). Spells of 7th level or higher are drained only partially and only on a 1, otherwise unharmed.

It never harms its host and guards it jealously, diving unseen to claw anyone threatening the caster (its normal attack) or slicing with its tail for 2d4. It blinks into sight while striking and then vanishes. Its AC is 5 for the host or a true seeing user, and AC 1 for everyone else during its strike.

Magic from others meets 75% resistance, and the host's magic 100%. It cannot foresee obvious spell effects, guess a caster's plans or identify spells being cast, so a host's non-attack area spell such as darkness can affect it if the spell is not absorbed.

A magebane trades up if it meets a mightier caster; otherwise its host is rid of it only by killing it. It rarely moves to another member of the same party, even a far stronger wizard, because it shuns past hosts. It needs only moisture, light, heat and magic, and exists solely to find and follow hosts. When two meet, both desert their hosts for a month-long mating, and four months later each hermaphroditic parent bears 1d3 live young.

Bat-hunting predators take magebanes when they can catch them. Alchemists and wizards use the flesh in magical experiments and will pay at least 400 gp for a carcass that is mostly whole.