Also if you want a really good idea of why League of Legends categories say nothing about the nature of the actual character
http://leagueoflegends.wikia.com/wiki/Cho%27Gath_the_Terror_of_the_Void
Dude is in the mage category. He's a giant bug creature whose attacks involve impaling you with spikes, screaming really damn loud, and eating you whole. Not very magelike!
On the other hand, this guy is a necromancer whose attacks involve summoning the undead that isn't in the mage category-- he's instead in the "fighter" and "melee" categories:
http://leagueoflegends.wikia.com/wiki/Yorick_the_Gravedigger
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No problem!
This is a cute and pop genocide of love!