Castle Ravenloft is the ancestral home of Count Strahd von Zarovich, the vampire darklord of Barovia. This makes it the centerpiece of every single iteration of the "battle Strahd!" adventure module that has made its appearance in literally every single edition of Dungeons & Dragons, and as such the entire Ravenloft setting was literally named in its honor.
As a result, "Castle Ravenloft" is often referred to as one of D&D's most iconic dungeons, and the speaker could be referring to any of the following modules:
- I6: Ravenloft - the original module, for Advanced Dungeons & Dragons 1st edition.
- RM4: House of Strahd - the tweaked version of I6 for AD&D 2e.
- Expedition to Castle Ravenloft - the Dungeons & Dragons 3rd Edition version of the castle.
- Curse of Strahd - the Dungeons & Dragons 5th Edition version of the castle.