This is the biggest exploratory Twine game I've seen since the Axolotl Project. Play as a spectre capable of shifting hosts who is seeking a black potion in the bowels of Castle Hallowmoor during a battle between witches and skeletons.
The game has 2-3 times the usual amount of links, with many of them descriptions only, so it is harder to cheat by clicking everything. There is an inventory button allowing you to dynamically use items throughout the game.
It took me about an hour, with some rather tricky pieces. Recommended for everyone.