I'd been holding off on this until I retired my current character, but now that I've got a clean install elsewhere on the drive I will give this a go today or tomorrow.
I thought about what should happen to Firemoth Fort after the mission. On one hand, it would make sense that the Legion would want to reclaim their lost fort, especially as it was considered a strongpoint in the Inner Sea. On the other hand, the Legion is in hard times, with the issues from Cyrodiil, and also there's a lot of secrecy surrounding Firemoth. The islands are visibly volcanic, so perhaps the atoll is unstable, too.
I also boosted the power of the Ward of Akavir, it's now a fairly decent medium armor shield with 50AR, and high luck. It now fits the relic status the Legion holds dear.
Here's the lore for Firemoth:
What one discovers on the expedition is that while the fort was used to fight piracy and smuggling, it was also an active part in smuggling too. This is why you find an ebony mine underneath the fort secured with a smuggler exit. Whether the East Empire Company was involved or not is uncertain; could very well be, keeping this secret from the Great Houses; but there was smuggling of the discovered ebony under the fort. What the Imperials didn't know is that the ebony found under the fort wasn't naturally occurring, and was used as a barrier instead. When the unearthed tomb was discovered, they opened Pandora's Box, and the fort was soon overran by undead.
The tomb was from more ancient times, it was used to trap the powerful necromancer Grurn in the past. The tomb was used specifically to bind the necromancer with ancestral spirits for his crimes, and the Dunmer then used ebony to encase the tomb to forever seal in the necromancer. The tomb and Grurn was agreed to be 'forgotten'. And perhaps was forgotten eventually.
Grurn eventually managed to break free from the bindings of the ancestors, soon dominating them to the necromancer's will. Grurn used the now corrupted ancestral spirits and remains to achieve great power, and become a lich. While growing in power, the ebony still restricted most of the lich's influence to inside the tomb. It wasn't until the Imperials set up fort that Grurn led the Imperials to the ebony, where the Imperials' innate greed took over from there. Once the mining unearthed the tomb, Grurn was free, and soon overwhelmed the fort with the lich's raw power and an army of undead, formed from the ancestral remains, and soldiers killed. As for what Grurn is up to now is a mystery, perhaps biding time, growing more powerful now that the lich is no longer confined to the tomb. It is known that the lich has a very large army of undead throughout the atoll.
The Ward of Akavir, a relic of the Legion, was on display at Firemoth, at the time. The shield was to be on display at the various forts in Vvardenfell to inspire the troops. The relic was lost when the fort was overran. The Knight in charge of Firemoth Fort was Sellus Gravius, how he wasn't court martialled for losing a fort as well as the relic didn't go unnoticed to the high-ranking Knights, but may be do to his connections with the East Empire Company and the Census & Excise offices... Sellus Gravius was only demoted a rank, and now is charge of the Census & Excise office in Seyda Neen. He is however still charged with retrieving the Ward of Akavir. Of course this is where the player and mercenaries come in. It's no longer official Legion business as the Legion has already sustained losses in regard to Firemoth, and to keep the unofficial business of the fort under wraps.