Frostwraith
The Demon King
like Pit, Dark Pit is an angel. Angels also originate from mythology, therefore, Pit should be excluded.
Mario, Luigi, Peach, Ness, Lucas, Marth, Snake, Ike, Roy and the Ice Climbers are all human beings.
Human beings originate from real life.
Therefore, they are excluded as well.
However, the argument above is flawed:
Mythology originated in real life.
Real life is life.
Life is a game.
Therefore, there's no problem in having such characters. Hades can be in SSB4.
Mario, Luigi, Peach, Ness, Lucas, Marth, Snake, Ike, Roy and the Ice Climbers are all human beings.
Human beings originate from real life.
Therefore, they are excluded as well.
However, the argument above is flawed:
Mythology originated in real life.
Real life is life.
Life is a game.
Therefore, there's no problem in having such characters. Hades can be in SSB4.