General

The Black Mage is not the only antagonist in the game

He delevelled the Hero class and introduced stronger bosses. In doing so, I say that he gives us a reason to play.

He was not connected to Phantom's skill nerf, nor was he connected to the Demon Slayer's nerf, nor the nerf of Mercedes. He was sealed away when the Heroes woke up.

And I doubt he can be connected to a future Luminous nerf or a Kaiser nerf.