The Secret Beneath Nighthorn Mountain

Publisher's blurb:

A thousand or more years ago, deep beneath the jagged mountains now known as the Nighthorn Ranges, a war between Dark Elves and Dark Dwarves overflows onto the surface - forces from both sides begin to utilize the lands above to travel unhindered and ambush their opponents.

It is nearby one of these ruins south of a town that you find yourselves, beside a wide river. In the distance to the east about half a mile, through a sparse forest up to the base of the mountain range, lies the top of stonework towers - the ruin of the fortress, overtaken by nature.