Sirius Black's concentration was momentarily shaken as a curse shot against the wall over his opponent's head. The purple jet of light shattered like a vase, sending harmless sparks down on Bellatrix's head.
Right, right; Bellatrix! Concentrate! She was his dueling opponent and cousin and most importantly, a threat to his godson. But not for long if he could help it!
Sirius narrowly dodged a curse that would have sliced his arm off and aimed an Expulso at her head. She ducked and twirled, yelling some incoherent spell, with light already forming at the tip of her wand when she about-faced and made a motion as if swinging a whip. He recognized the spell and put up a hurried Shield Charm as a golden chord swung towards him, arched over the shield, and cracked like a bull-whip just near his face.
Grinning widely at Bellatrix's obvious displeasure at not having even touched him, Sirius aimed a high Disarming spell to distract her and touched the ground with his wand while she wasn't looking. The floor rippled towards her at lightening-speed and the wave knocked her off balance. But before Sirius could put a Full-Body Bind on her, she had recovered and quickly made it necessary for him to duck a Stunning curse.
All in all, Sirius had missed this feeling so much.
Euphoria was what it was. Sheer terror, copious amount of pumping adrenaline, raw pleasure at venting out frustration, and delicious triumph with every hit; there was nothing like taking your life in your hands with a duel. And after being pent up inside for months, almost an entire damn year, this was almost too much excitement to handle.
Knowing he could beat her was the best part. They'd dueled in school a few times, she being only few years older than he but those scraps had typically ended in draws. However, in the early days of the Order, once he'd gotten older and better at dueling, he'd arrived on scene countless times to a Death Eater attack, only to find her torturing some Muggle or cackling as she surveyed the damage of a half-destroyed neighborhood.
He'd nearly beaten her almost every time (and fine, so maybe James had usually helped…but just a little) but every fight, just as he was going to give the final blow, something to knock her out cold for the Ministry to pick up like trash and anchor her to the spot so her little devil friends couldn't Side-Along her in a pinch, the Order had to evacuate.
Or a nearby explosion knocked them both to the ground and she escaped.
Or over her shoulder he saw Pettigrew getting his ass kicked and needed to step in.
Or James shouted his casually comical, "I'm in need of assistance!" only for everyone to look up and see that he'd dove straight into where the fighting was at its thickest, had his back against a wall, was dueling four enemies at once, and desperately needed someone's "assistance".
Or (and this only happened once or twice) one of the other Death Eaters came to her rescue. (And most likely, was promptly Obliviated on their return to headquarters so that he would never tell the others that the infamous Bellatrix Lestrange had been in a bind.)
But not this time. This time he had her. This time Sirius would have her knocked out, trussed up, and packaged with a fancy bow. Perhaps the display would be enough to convince the Ministry he was innocent. He would give anything to see the look on Fudge's face as he, Sirius Black "wanted felon," delivered Voldemort's Second-in-Command over to him like an early Christmas present.
He smiled again at the thought as he dodged another badly aimed curse. Her frustration was making her sloppy and it was sweet justice to see her angry grimace to know that he was winning. He'd hit her once in the leg, though that was when he'd engaged in the fight and had the element of surprise on his side, but the fact remained that she had yet to wound him.
With a scream of indignation at his knowing smirk, she sent a Stupefy that over sailed his head by almost a meter. Sirius had to laugh at that. Because oh, these skills of hers were becoming just pathetic.
'"Come on, you can do better that that!" he yelled, his voice echoing around the cavernous room.'
With a snarl and a twist of her wand that was too fast to react to, a jet of green light came speeding towards him, aimed for his chest. He recognized the curse, knew he'd overstepped himself with his jeers and this was the result of his folly, briefly wondered about Harry—damn it! What had he just done!? Leaving poor Harry like that—and felt the second jet of light hit him squarely in the chest.
His vision tunneling, numbness traveling rapidly through his body from his extremities towards his chest; Sirius Black's body tumbled backwards through the Veil and disappeared.