Alex Black is possibly the most powerful wizard of his day. A Metemorphmagus 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 it suprised me to see a snow leopard meander in." - The Records of Albus Dumbledore, 1982
Born a snow leopard in the mountains surrounding Hogwarts, magic formed a layer underneath his skin allowing Alex to beacome 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 1981. 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.