Alex Black is possibly the most powerful wizard of his day. A Metemorphmagi and Animagi from birth, he was born with the ability to apperate and disapperate at will with disregard for charms.
"I was sitting in my office thinking, when all of a sudden I heard voices at the bottom of the stairs. I quickly realised that one was the gargoyle who watches my office and a child. Soon the staircase began to move and a mewing sounded at the door. I happily obliged to open it and was, I confess surprised, me to see a snow leopard cub meander in." - The Records of Albus Dumbledore, 1982
Born a snow leopard in the mountains surrounding Hogwarts, magic became part of him, allowing Alex to become a human and a cub whenever he wanted to. As having a human Soul he aged much slower than his mother and was still a cub when she died in 1979, three years after his birth. He cared for himself as a human and a Leopard, stealing food from the Hogwarts kitchen and enjoyed annoying Mrs Norris, whom he disliked intensly. These occasional forays into Hogwarts lead Alex to Dumbledores office. After a couple of minutes of observation, the cub curled up on the end of the headmasters bed and slept.
Between 1982 and 1988, Alex was raised by Dumbledore resulting in a utterly complete knowledge of Hogwarts to match Harry Potter, Voldemort and Dumbledore himself. He achieved Ten O's, In Ordinary Wizarding Levels and became only the fourth in history, after Minerva McGonagall, John Dawlish and his foster father to achieve full marks in his NEWT's.
"He didn't want to attend school, because he already knew more than most who leave Hogwarts in thier Seventh Year, besides he had already taken his exams. I wanted him to spend time with others his age, but in my heart I knew he was more Leopard than human, plus I didn't want to find Mrs Norris strung up by her ankels as rusult of some bloothirsty, non-human spell as he was prone to cast. Alex often stormed off and hid in the grounds or mountains for a few days before he skulked back and apolagised. After the fight we had on the day he got the results for his NEWT's and I said he would go to Hogwarts he ran away for a months, returning on August the 31st. He didn't go to school, but in the years following he often told me of any events I had no knowledge of contributing to my air of omniscience. He could blend into a crowd of students as I could not, and it became a invaluable gift in 1992 and 1993 with the events concerning the Chamber of Secrets." - The Records of Albus Dumbledore, 1993