A quick look at what it means to be a Conduit, for some worldbuilding and because I plan on taking the concept outside of the fantroll scene later.
As described in Enrise's profile, a Conduit is someone who serves as a sort of "hive" for the fae Unkind. How a conduit is selected is unknown, but one day the crows will select a young troll and spirit them away from their lusus to parts unknown, using their beaks and claws to cut into their skin the tattoos that will allow them to harness magical power unthinkable to an average wizard.
But don't expect to be able to copy them for your own benefit. The tattoos alter themselves, shifting painfully about on the skin and keeping the unfortunate conduit in a constant state of soreness that painkilling spells do little to sooth. At best, anyone studying the tattoos will be able to increase their capacity to store mana by a small fraction of the amount a conduit can, but for most practicing mages this is usually enough. Conduits, however, have infinite (or so high it might as well be) storage capacity for mana.
Which is good, because the Unkind never stop bringing in more. Like bees, they fly out and collect things. People who voice their spells leave echos that need to be cleaned up. Ritual sites need to be scrubbed clean of radiant magic. Places where casters regularly practice need to be pruned and trimmed to keep the buildup from becoming dangerous. Many spellcasters do not even realize what the Unkind do, only that they're drawn to their acts. While the Unkind do deal in trading knowledge, and can even act as teachers, their primary function in the court hierarchy is gathering up stray magic to make sure it can't get up to anything it shouldn't.
Conduits store these fragments and lost spells in themselves, expanding their spell libraries further and further as the spells burn new marks into their skin. To continue with the beehive metaphor, these fragments eventually shed their "impurities" and become raw magic. Magic in this state is a force of nature, uncontrollable and mindless as we understand it, but still possessing a strange will of its own. The sigils and glyphs keep the magic from outright destroying the host, but the simple process of restraining it has been likened to having "a balloon inside you, constantly inflating and pushing out," and it lashes out against its "prison," casting spells taken at random from the conduit's mental and epidermal library.
It cannot harm the conduit directly, but the raw magic seems to possess a cruel sense of humor and delights in the smallest excuse to cast a spell relevant to their situation, though the power level of the spell and what it does can vary wildly. Because they cannot control what is released, nor can they tell what will cause the magic to lash out (it could be anything from their lives being in danger to a certain set of words being spoken), conduits do not often make connections with others of their kind. This is not to say they can't, as the only restriction the Unkind have towards public relations is that they do not mingle with other conduits, and in fact many conduits do form friendships and even quadrants to help ease their situation.
Conduits also have limits on how much of the magic they have access to. They can perform spells themselves to help get through their life, but to put it in D&D terms they can only use level 0 and level 1 spells, but can use them endlessly rather than a few times per day. Everything above 2 is restricted. If they had full access to the power they held in their body, a single conduit could very well shift continents around, the very thing the Unkind are trying to prevent by shoving all that stray, untapped magic into an easily-controlled, easily-locatable, easily-transportable source. Even using simple spells but pouring incredible amounts of mana into them to make them several magnitudes stronger than intended is carefully restricted.
Before a conduit dies, the Unkind steal them away to parts unknown once more. All the magic they held is passed down to the next troll taken, all the spells they've ever learned are passed as well. Well, not all the magic. The higher-ups in the court take their own shares, sips, and nips, as well as confiscating any spells they don't want wandering the world, ready to go off at the slightest provocation.
The Unkind occasionally take their own share of the sweet honey as well, invading the unfortunate conduit's body as they recharge or carve a piece out of the mass to take to one of their many students. Sometimes they even craft an entire spell and pull it out for later use, which feels unpleasant but lessens the pressure of the building energy somewhat.
