Voldemort was dead.
All dead.
This time, not the partway, still-able-to-come-back-if-certain-measures-are-taken dead that he had been for the majority of the Golden Trio's lives. No, this time he was as gone as your bald uncle's hair –not even a healthy dose of Rogaine could return him to his prior glory.
The famous boy-who-lived and his less famous entourage made sure of it. In the epic final battle, the very one that had been strongly alluded to from page one, the three of them –Harry especially- destroyed Voldemort, his body, and, through intricate spells and an immense display of powerful magic, his soul. Well, as much as anyone can destroy a soul, but to the layman, what they did was to that measure.
This occurred at the end of their sixth year at Hogwarts. Of course, this meant they missed their NEWTs and OWLs, but there was really no question that they should proceed to seventh year with the rest of their dazed classmates.
The summer following their sixth year was a time of recovery for the Golden Trio, and for the Wizarding World as a whole. Aurors spent the three months hunting down Death Eaters that had survived the final battle, while Harry, Hermione, and Ron stayed at the Weasley house and tried to gain as much normalcy as possible before returning to school.
By the end of summer break, the threat of Death Eater retaliation was almost completely removed from Great Britain and Europe as a whole, and for the first time in several decades, muggles and wizards alike could live without fear of torture and death at the hands of Voldemort's followers.
Unfortunately, there were still some major Death Eaters that managed to stay under the radar. These primarily resided in North America –more specifically the United States-, where they could reconvene with less concern for the Ministry's long arm of justice.
One family was a particular threat, their reputation for power, cold-blooded crime, wealth, and underhanded dealings reaching to even the most common British wizard. It was rumored that the head of the Kiasin household provided much of the funding for Voldemort's attack, and had annihilated many of the Ministry's strongest Aurors when they dared to 'sniff around' his territory. The United States was a weak point for the Ministry largely because of the Kiasin influence, and for that reason, many important Death Eaters eluded the Ministry's grasp by seeking refuge in the Kiasin mansion.
The Kiasin 'empire' had been building for a long time now. Pre-Voldemort, Nikolas Kiasin Sr. was developing steam. His family inherited large sums of money, only adding to the wealth he already had. He saw Voldemort as an opportunity to pursue his goals with as little effort as possible and became one of his first influential followers almost immediately. He provided money, magic, and allies, all very appealing to the Dark Lord.
His son maintained this loyalty, playing Voldemort's indispensable follower while he waited for an opportunity to take Voldemort's plans to the next level. The Kiasin family maintained a position where they could take advantage of either result –whether Voldemort won or lost, they were determined to take control of the Wizarding World far more efficiently than Voldemort ever had, and they had the means to do it.
Of course, the Kiasin family was a distant threat to the students at Hogwarts. They were across the Atlantic, a family to be hated, sure, but nothing compared to the utter terror that Voldemort had inspired in everyone. Voldemort was dead now, gone forever, and his followers were just that -followers. It was like a snake with its head cut off-in its death throes but no longer armed with venom or fangs. No longer operating with a brain or a leading force, it was to be considered and dismissed. Only the Aurors and choice members of the Ministry fully understood the implications of the Kiasin family's power. The Golden Trio had dealt with enough-it was time for them to live their lives as seventh years at Hogwarts.
And as for the Kiasin family...an inside force soon brought them crashing down, but even then, they were not a family to defy.