Lair of the Frog King is a short adventure for five 1st-level characters that takes place in an ancient castle. The river—which used to flow around the castle and fill its moat—has diverted over the centuries, and now what used to be fertile farmland is marshy bog. What’s more, the swamp has claimed the castle itself. A tribe of bullywugs settled in the muddy former fortress, and use it as a base to raid nearby farms. Can the newly-minted heroes stop the bullywug menace? Find out in Lair of the Frog King!