Kelibroth, Undead Menace

Publisher's blurb: The Drag & Drop series delivers content DMs can insert into their already existing storylines to add to what’s already there, or to help find somewhere else to go with their party. The only thing you need to add this into your current storyline is: Something that has been killing people, especially in large groups all at once. This could be a war, a recently-caught serial killer, a plague.