You keep yelling telepathic orders to Beirus, but minor decrease in your power tells you that he's starting to get over it. A minor setback, but not enough to change obvious outcome.
There is too much fire between you and Beirus, you can't tell his exact location within the fireball. But it doesn't matter either, you have enough firepower to fill it with holes. At the same time as you begin firing the spikes at the fireball, it starts floating up. The spikes are not slowing down on their path through it, so you can tell you missed him. That's fixed easily enough. You keep shredding it more, but only thing that changes is the fact that the fireball stops ascending.
Then it comes down.
Fast.Fireball expands across ground like a tsunami, burning your organic wing into crisp and rendering its mechanical counterpart unusable. Despite of your mechanical demon body you are not fireproof, so all thinner parts take some damage. There aren't many such parts however, so overall damage is minimal, only your eye pairs facing fire melted a little. All you need to do is to turn around and continue as if nothing happened. A shockwave follows the fire, and few seconds later metal pieces whizzes past you colliding the pillars behind and around.
Fire recedes and lets you finally see Beirus again. He's floating in air in his whole
Nightmarey glory, some 150 meters up, and he's missing one of his legs from knee down. Unarmed as far as you can see. Looks like he lost his shit for your copy. Also, now you can aim him.
Still yelling nonsensical orders into his mind you play with him, driving your earth stakes through his legs and arms, pinning him on the sky. You laugh at him, insulting his broken body, and he laughs back.