A great many of the deeds of so-called wizards are in reality nothing more than those of pokemon concealed by their trainer. For instance, the "fireball" spell is little more than waving one's hands and shouting incantations while a well-placed fire pokemon uses fire spin. The real wizards of this world can not be found among humans or among the living, for it is the Mismagius which are truly capable of practicing magic.
The meaning of "magic" itself has narrowed considerably over the years, as attacks and mysteries once attributed to it have since been resolved by science. But the mysterious incantation-based techniques of Mismagius (and their songs of death, which are shared by Lapras and a few others) have defied every paradigm and theory that has been ventured to explain them and every principle on which science rests. From summoning people and pokemon from across the planet to reversing entropy and raising the dead, Mismagius' strange powers defy explanation and natural laws, but are bound by their own bizarre set of rules; most importantly, that they may never be used in battle.
It is the sympathy of the gods, not some tome of hidden literature, which has given the Mismagius these powers, for their spirits must suffer greatly from a lover's betrayal to become a Misdreavus, and bathe in utter darkness to evolve into this form. Yet there have always been those cruel and ambitious enough to seek the power of magic at any cost, even if they must manipulate those around them into hating those they love. Even at the cost of their own lives.
It is one of Arceus' cruelest tricks that only when they gain the power of magic do they realize what an awful burden they now bear.