There is a war going on. It has literally been going on for ages and centuries and more generations than anyone can count. It's been passed down through the generations of these two lords. Lord Zhentarim and the Lord of the Order of the Gauntlet or something. Nobody is quite sure how it started. Some prophecy or somesuch. But neither army has yet been able to triumph over the other. And so the war continues. It has evolved into a territorial war for appropriation of the islands hereabouts and the waters surrounding them.
These islands don't even seem to be that important in the grand scheme of Faerun. There are wars between gods raging on the major continents. These islands, South of Zakhara (the closest major landmass) aren't even on the main drag of the crowded sea. They're mostly scarce of people due to the fighting and general lack of big cities nearby. There are some larger ports scattered around, and that's where the majority of the population lives. The rest of the land though is left to the pirates and wild beasts. In some places there are remnants of grand civilizations, but they are long since gone, and all that remains are ruins of once-great structures.
Between the Pirates and warring lords, the islands have fallen into disarray from the sunny trading ports they had once been. I remember traveling between ports with my family and fellow traders very fondly. But the war divided the people, and the fighting ships have been so preoccupied with sinking each other that the pirates have run rampant in the area. That's how I lost my family. Since then, I've been training as a cleric and working to help the islanders restore their cities to the beautiful ports I so fondly remember, while seeking justice against the savage pirates wreaking havoc on the area.