The Moonshae Trilogy

The Moonshae Trilogy is a series of novels by Douglas Niles, set in the Forgotten Realms campaign setting. "Darkwalker on Moonshae", the first novel in the series, was the very first Forgotten Realms novel ever published.
Plot summary.
"The Moonshae Trilogy" takes place on the Moonshae Isles, and involved a young prince on his way to unite all the people on the islands.