From publisher blurb:
Elite Enemies – Sahuagin provides the Game Master with twenty ready-to-use Pathfinder Roleplaying Game® compatible demon-related stat blocks, one for Challenge Ratings 1 through 20! Variation and challenge is achieved through a combination of class levels, simple templates, and advanced templates. Each stat block includes a convenient name, some background or history, a complete stat block with adjustments for class and templates as well as equipment, and a summary of combat tactics. Use the stat blocks individually to make memorable NPC villains or combine them to quickly generate themed encounter groups. Using this product, you always have a collection of demonic opponents to unleash upon your characters regardless of the party level!
This product heavily utilizes materials available in the Pathfinder Roleplaying Game Reference Document combined to provide new challenges and interesting foes.