Moody gave him no chance to catch his breath.
"Impedimenta!"
"Stupefy!"
Spells came like a dense shower of rain from every tricky angle, forcing Harry to roll and dodge clumsily.
"Real combat isn't a turn-based game, Potter!"
Moody's roar echoed through the Academic Affairs Office.
"The enemy won't kindly wait for you to finish your incantation!"
"Use everything around you! Your feet, your brain, and your opponent's ridiculous arrogance!"
Sirius's brow gradually furrowed.
He could tell something was wrong.
He knew Alastor's fighting style well.
Forceful, direct, full of the suppressive power of a conventionally trained Auror.
But the Moody before him fought more deviously, more lethally, and he even saw urgency in him.
Several times, his spells skimmed past vital parts of Harry's body at angles too vicious for training.
He stepped forward, ready to intervene.
"Let me spar with you, Alastor. Give Harry a breather."
Moody turned his head, his magical eye fixed on him.
"All right."
The duel between the two top-class wizards began in an instant.
The light of their spells illuminated the entire office.
Sirius soon confirmed that his instincts had been right.
Moody's attacks were ruthless and unpredictable.
During one defensive move, he even instinctively used an extremely obscure piece of Dark Magic with a mild corrosive effect.
Though it vanished in an instant, Sirius still caught it.
"You've had quite a temper lately, Alastor."
Sirius sounded him out as he used an exquisite piece of Transfiguration to turn an incoming jinx into a flock of canaries.
Moody snorted coldly.
"You can't show Dark Wizards the slightest mercy! Not even in training!"
He put it down to Moody wanting to place Harry under greater pressure, to prepare him for a real battlefield.
Perhaps it had simply been too long since he had last fought