Addictive Magic

Sometimes magic is not just something someone can do, it is also something that is physiologically and mentally addictive. People who use Addictive Magic always want to use it as much as possible because it feels pleasurable to them in some way. Sometimes there is a risk to the user if he uses his magic powers too much, and so he must be careful about using their powers too often, lest they consume him. In extreme cases, it might even be a Fantastic Drug.

Compare The Dark Side, where evil is addictive.

Comic Books

 * Black Adam in the Captain Marvel storylines.

Literature

 * Skill-users Robin Hobb's Realm of the Elderlings books suffer from an addiction to Skilling that can cause truly terrible physical pain and mental distraction. Fitz suffers especially from this addiction.
 * Channelers in The Wheel of Time must be careful not to hold on to the One Power too regularly. Doing so can encourage a person to draw in more and more. Left unchecked, a channeler can overtax his abilities and burn out his ability to channel or even kill himself. Fortunately, a slight exercise of will can control the desire to channel excessively.
 * Using the True Power is even more addictive; using any noteworthy amount of it nearly guarantees that a person will eventually overdraw and die even more messily than if he had done so with the One Power.
 * In the Dragonlance series of novels, it is said that High Sorcery can be like this for some people. Raistlin Majere was one such person for whom using magic felt good. It is described as something the high sorcerer can feel all throughout his body when he casts a spell.
 * In The Dresden Files, this applies to black magic, which is why the White Council kills anyone who uses it even once.
 * In Neal Shusterman's novel The Eyes of Kid Midas, the protagonist becomes increasingly reliant on the power of his magical sunglasses. The sunglasses aren't in any hurry to go away either.
 * Warlocks in the Ethshar series qualify — the more they use their magic, the easier and more pleasurable it gets. But the power's drawn from an external source, and a warlock who uses too much ends up being irresistibly summoned to that source.
 * A recurring theme in the Shannara series, though more for some magics than others. The Sword of Leah is perhaps the most consistently addictive.
 * Subverted in the second Mistborn novel. Straff Venture assumes that using the mystical metal atium to fuel their powers is addictive to Mistborn, and uses carefully controlled rations of it to control his Dragon  Zane. Atium, however, is not addictive (at least, no more addictive than anything that grants power), and Zane mentally derides Straff for thinking so- he hangs around him mostly because he doesn't have anywhere else to go.

Live Action TV

 * Willow's magic in Buffy the Vampire Slayer. It was later subject to an Author's Saving Throw that denied that magic itself is addictive.

Film

 * In The Covenant, the Sons' magic is not merely highly addictive, but drains their vitality and prematurely ages them the more they use.

Tabletop Games

 * The Third Edition Shadowrun supplement "Magic in the Shadows" introduced "focus addiction". If mages used foci too often there was a risk of their becoming addicted to and dependent upon them. This could cause them to become unable to use magic without a focus or even lose their magical abilities altogether.

Video Games

 * The Blood Elves in World of Warcraft became addicted to Mana. As High Elves they were able to draw on the energies of the Sunwell to sate their addiction, but it was defiled and tainted by the Scourge. The main schism between High and Blood Elves arose because they disagreed over the best way to cope with their condition. High Elves prefer to meditate and master their cravings and Blood Elves started finding other sources on which to feed - including demonic energy. Some of them were able to control that addiction; some of them were transformed into wasted, addicted beings called the Wretched.
 * Notably, becoming addicted to magic is the only way a male Blood Elf (or female for that matter) can go bald - making it a literal Bald of Evil.
 * Strictly speaking, all mortals can become addicted to arcane magic in the Warcraft setting. The effects of casting an arcane spell are described in terms that make it sound a lot like real-world drugs and mages may feel the urge to cast the spell again for the thrill it causes. The MMO even makes a joking reference to real life anti-drugs campaigns with this in-game book: (contents are posted in the comments).
 * Even more dangerous is fel magic - that is, demonic energy - which is even more addictive and MUCH more corrupting.

Web Original

 * The mysterious mage of The Questport Chronicles, becomes increasingly reliant on the essence of Aether to counteract his Amplifier Artifact, leading to a rather unfortunate end.