Sisters of the Dark Mirage (2016)

Publisher's blurb:

Lost in the mists of the Dark Mirage, the players must deal with a trio of witches that dwell in this strange place in order to escape.

Sisters of the Dark Mirage can be completed in a single session, making it a great standalone, one-shot adventure, or it can be included in any longer running campaign as a stop along the way. It shines most as a set encounter during your Out of the Abyss campaign, as your players travel the Dark Lake, and its themes fit the style of Ravenloft well, but it can be easily inserted into any campaign, and is easily adapted to other locales like an eerie swamp. The adventure is designed for 4-6 player characters of third level, but includes notes on modifying encounters for more or less powerful parties.