A four-hundred-and-fifty-year-old Sicilian witch who reads the cards, and who stays behind so the others can leave.
Lilia Calderu is a 450-year-old Sicilian witch and a member of Agatha Harkness’s coven. Patti LuPone plays her, and Chloe Camp plays her young. Wikipedia’s article on Death records that Death, in non-human form, appeared to Lilia when she was a young woman in the 1500s. The reader who sent this list described her as the premonition witch who hid Billy’s true identity from everyone, which is the kind of thing a divination witch knows and does not say.
Minor spoiler
After Agatha, Jennifer Kale and Billy Maximoff escape the fourth trial, Lilia decides to stay behind as the Salem Seven close in. She flips one of the cards, the entire room turns upside down, and the Seven are impaled, and presumably she is too.