Abysslin, Cave of Ungutu is an excellent "side trek" mini adventure set in the savage lands of the Olman. Abysslin writes:
"Long ago there was a vast empire overseen by Emperor Zotlatlan. He was a tyrannical ruler in every sense, but his people led full and bountiful lives. When Zotlatlan moved his ambitions to the conquest of the surrounding tribes, they rallied together under the leadership of the Lizard Tribe, whose chief slayed Zotlatlan."
Cave of Ungutu is designed for 1st/2nd edition AD&D rules so that makes it easy to adapt on the fly for any version of the game. It's a quick and deadly setting to run with some unique monsters, magic items and even a map included. What more do you need? Enjoy!