The Demon Slayer's Plight

Has anyone else not noticed this but "Forest Gump: But Lt. Dan, you ain't got no legs." Right before the Demon Slayer does his power up the black mage surrounds himself in energy and the robe opens up to about mid-level and he doesn't have legs. This leads me to believe that either A: S/He's just a floating mass of evil. Or B: S/He's only a puppet. Also if S/He is only a puppet doesn't that mean we will get to face it, and it'll still leave an even bigger baddie in the midst.

It kind of reminded me of Ergoth really. Watch, we get the Black Mage boss, and it's just an Ergoth recolor without the staff.