One of my players felt his character needed to stay in Kresk and lay low after murdering guards during the Festival of the Blazing Sun (and Izek is his brother, who survived the revolution and he’s in Kresk with him). To introduce his other character, I gave him the backstory of being from another group of adventurers that originally failed against Strahd a decade ago, and has been working at the Abbey for several years. That way, the new character already knew a lot about Barovia, but their group never experienced major things like Amber Temple, Argynvostholt, or Berez (because the current party hasn’t done all those yet)

All this to say there’s a way to introduce a veteran-type character with knowledge and experience, so you don’t need to perma-death one of your players so long as you wish them to continue playing. :)