I'll take some pictures from my manual when I get the chance... it's kind of worn, I read the hell out of it as a kid.Pokun wrote: King Koopa is described as Daimaou Kuppa (大魔王クッパ) in the manual, which means Great Demon King Kuppa (a very common title for villains in fiction). It does say they are capable of powerful magic, but so does Peach who is the only one that can counter the curse. Koopa is a turtle demon that can probably do demon magic but I think wizard sounds a bit weird. Where did they say he is a wizard? In the English manual they just say they are using black magic.
But yeah besides turning the Mushroom people into bricks in SMB they don't seem to use a lot of magic anymore? Koopa uses things like power stars in SM64 to create new worlds or the star rod in Paper Mario and so on, but I don't remember him using his own magic.
One other thing it mentions that I remember clearly is how all the people of the mushrom kingdom have been turned to stone by said magic, so when Mario is breaking the blocks he's supposedly freeing them or something?
I thought it was really cool when they kinda revisited that in the Nintendo Power comic by Charlie Nozawa, which was also brought in magazines over here:
In general, that comic was all kinds of cool, and works surprisingly well with where Nintendo have taken the Super Mario "canon" since then.