A Level 7 Monster Card that can be obtained through Yugi's Starter Deck and spellcaster-themed decks. There are various versions of Dark Magician, in which the spellcaster's hair is different-coloured and poses vary.
In the manga and anime, Yugi often uses the Dark Magician against various foes, making it his signature monster card. When in a duel against a strong foe (Maximillion Pegasus), Yugi often 'evolves' Dark Magician to stronger forms using ritual and spell cards. The Magician of Black Chaos and Dark Magician of Chaos (Dark Magician was sacrificed with Jigen Bakudan) are examples of its more powerful forms, along with Sorcerer Of Dark Magic, Dark Sage and Dark Eradicator Warlock.
In the Trading Card Game, this card is pretty weak, since there are many cards with more ATK and/or useful effects that also require 2 sacrifices to summon. To account for this, many cards were released with superior effects with Dark Magician as a requirement to play e.g 'Dark Magic Attack'. Also cards that make the Dark Magician easier to summon, such as 'Skilled Dark Magician', help keep the Dark Magician just about useable.
There is another Dark Magician type monster called Dark Magician Girl, which Yugi starts using in the Battle City arc of the manga and anime. Whilst it is weaker than Dark Magician, it gains attack points for every Dark Magician in either Graveyard.
In the final arc of the manga and anime, a priest named Mahad served under Pharoah Atem, using the Millenium Ring. In a fatal battle against Bakura, he allows himself to be killed so his spirit can become the Dark Magician. His apprentice, Mana, later becomes Dark Magician Girl.
A Dark Sage named Torunka appears in Yu-Gi-Oh! 5D's, albeit his age is reverted to that of a child due to a curse.