“Right,” said Amanita. “Because they need to go back and repair them from time to time. Objects like that crystal-” She patted her saddlebags. “-can’t hold souls the way bodies can. They fall apart on a metaphysical level, the soul disperses, ding-dong, the lich is dead. I mean, if phylacteries didn’t require some kind of upkeep, a lich would just stick her soul in a needle in an egg in a duck in a hare in a box beneath a tree on a phantom island or something and nopony, including her, would be able to find it and use it to kill her!”