Mages are the purest spellcasters, in a way. They do not entreat or bargain with elemental spirits (yet they can summon elemental power, after a fashion), they do not invoke the Holy Light or the Shadow that opposes it, and the fel magic that drives warlocks does not interest them. Mages seek the purity of absolute arcane knowledge - knowledge untainted by dark pacts or the promise of a glory gained if one follows the precepts of an unknown and unknowable philosophical force. Mages don't bargain, they don't plead, and they don't even compel - mages understand.
Magic is a tool, some would even say a gift. But you should never forget its fundamental nature. Arcane magic twists the boundaries of our world. It weakens the laws of this realm to allow the impossible to happen, if only for a moment. That single moment is all a demon needs to wreak havoc. The Burning Legion has watched us for millenia, always waiting for the smallest rift to slip through, the smallest stirring to whisper from. Remember this, young ones. Every spell you cast, no matter how minor, cuts both ways. This is why sorcery must never be used frivolously.
- Vestia Moonspear
Now, this obsession with arcane power and knowledge isn't always for the good - many lore figures like Archimonde and Kil'jaeden began as mages before turning to the dark and corrupt path of the warlock. Azshara, queen of the Kaldorei, was (and likely still is) a mage of enormous power, and we need look no further than the recent Nexus war to understand that mages and the magic they seek to understand can have devastating consequences for all. Azeroth, for better and for worse, has been shaped and defined by arcane magic.