Siege at Firemoth adds a small island chain southwest of Seyda Neen, and a small quest involving taking out a large army of skeletons.
Unlike most areas in the game, this place is very combat-oriented—you may find yourself facing dozens of enemies at one time. At the end, you will face Grurn, the leader of the island's undead, and a powerful lich to boot. You will be rewarded with the Ward of Akavir, a shield with a constant effect Fortify Luck enchantment.

INSTALLATION
Extract the contents of the archive into the Morrowind/Data Files directory.

Official Plugins will not invalidate your old saved games. If you save your game while this plugin is loaded, you may encounter error messages when you reload the saved game without the plugin. But you will be able to continue on with the original game.