X9: Savage Coast
X9: Savage Coast is an adventure module for Dungeons & Dragons (Original), released in 1985. Set in the Mystara setting, it's a fairly simplistic (the booklet is only 32 pages long!) wilderness crawling adventure, set on the Orc's Head Peninsula off of Mystara's Savage Coast region. The entire plot can literally be summed up like this:
In the safe, seaside town of Slagovich, the player characters set anchor and stay at the inn, where they hear stories of Orcs Head Peninsula. Lost cities full of hidden treasures, terrible beasts and cannibals roaming the coast, gold ore piling up at the mouths of rivers, and a secretive religious sect. What would motivate the adventurers to enter the uncharted jungles of the Savage Coast—curiosity, a desire to help others, or simple greed?
The region would be fleshed out in Advanced Dungeons & Dragons; first in passing as the Red Steel setting, which actually takes place in a specific part of the Savage Coast, and then as part of the Odyssey line, which would release a Savage Coast campaign setting splatbook (with Monstrous Compendium Appendix) and a pair of Orc's Head Peninsula splatbooks (the Sourcebook, which combines an atlas and rules for generating native PCs, and a book of adventures).