When he’d ever had the time to research and develop such spells, she never knew. Perhaps they had been passed on by Voldemort...perhaps he had found them within some ancient and forbidden book on dark magic...perhaps he had taken it upon himself to learn and craft them in that year after he had killed Dumbledore and gone into hiding from the world.  He had told her years ago that he had in fact trained under Voldemort and his aunt to grow his power, but he said nothing else about what he had done in that time, and, sensing that it was just as horrific as his other actions, Pansy had never pressed further.