Giuseppe di Cattivo (1450-1518) was a contemporary of Leonardo da Vinci and a fellow artist, as well as his neighbour.
Giuseppe di Cattivo was renowned for the disturbing nature of his paintings, for which he became known as "the Artist of Nightmares". At one point in his life, he found a sentient meteorite and used its minerals as a material for his pigments. Using this paint, he created his masterpiece, called The Abomination, and lent some of it to Leonardo for one copy of the Mona Lisa (the copy that was eventually put on display in the Louvre, Paris).
The Abomination, however, was too terrible to lay eyes on without going mad. Gripped by fear, di Cattivo locked the painting in a vault made of wood from the hangman's gallows, with a Mystery Chinese Puzzle acting as the lock. The following morning, he was found in his Florence apartment, completely insane. He ultimately died in a lunatic asylum.
The International Gallery of London took possession of a collection of his works in Victorian times, and stored them in the vaults in the basement. (TV: Mona Lisa's Revenge)