There's some information - there have indeed been many, many media reports about them - but not much in the way of solid info. No one knows who they really are, or where they are now, because they disguise their appearance. Two years ago they succeeded in impersonating the Prime Minister, but was ultimately foiled when the Plucky Orphans accidentally broke through the enchantment he'd put on the real PM to make him look like a vagrant by accidentally setting the PM on fire.

There are many, many wild and ridiculous conspiracy theories about the Dark Magician.

As for the known history of magic, it is there. But it's possibly a bit tricky to find, since it's actually included in the history of art section. (Since, as far as the people of this world are concerned, they're the same thing - sure, people can and often do create non-magical artworks - but magic is still very much regarded as the same thing as art.)

Edit to make this more clear: basically, the history of magic is the history of art.