Madam Eva is a mysterious vistani fortune teller who seems to have a special connection with Barovia and Strahd. She performed a tarokka reading for the Waffle Crew which helped them figure out a way to defeat Strahd. 
When the Wafflecrew travelled to Barovia's past, they met a young woman named Katarina. They learned that she was, in fact, Madam Eva. It was later revealed that Madam Eva had pulled Strahd aside and told him that the Dark Powers wanted to make him immortal.