Alliance Raid ramblings spoilers for post Rank 5 of San d'Oria missions, part of Wings of the Godess and San d'Oria WotG nation quests. Sorry if I get full on whose Pepe Silvia.
OK so I think I figured out who Alxaal is meant to be and I feel that he's Rochefogne. He starts off as a semi mysterious figure in the rank quest lines until one day he straight up all you're going to cause a calamity and yells at the adventure. You later on find out that he is the late Queen of San d'Oria's brother one Rocgefogne I Tavnazia.
Tavnazia is an island in present day Vana'diel. It wasn't always this way. To most in present day Vana'diel the way this came to be is the orcs used the equivalent of a nuke during their attack on Tavnazia that which caused it to become physically separated from the rest of the land. This made them loose almost all contact with the main land.
Now what you learn either via the San d'Oria missions in the past or through the main story of Wings of the Godess I can't remember is that it wasn't the orcs but San d'Oria itself. They found this sword that has ungodly powers (don't ask how it got forged). So ungodly that you could think of it as Mjolnir in that only a certain type of person can wield it. We get to the point in time when the attack on Tavnazia happens during a mission in the past and the super weapon is the damn sword itself. The weilder if I remember right only unsheathed it which causes a beam of light to shoot from the sword. It not only saved Tavnazia but also caused said separation.
In present day San d'Oria the sword dubbed Lightbringer had been stolen and was about to be found by the orcs in a desperate attempt to restart the crystal war (this is an almost constant thing in XI. Just like how Odin has some kind of involvement in any of the major story lines) but we know that in the past the sword was "lost" on purpose with a swearing to secrecy.
Now Rochefogne found out about what really happened 20 years in the past so knows what Lightbringer is capable of doing. Thankfully the attempt to just unsheathe the sword is averted. As somehow it got tied to the San d'Orian royal line of succession where only the true heir to the throne would be able to wield it.
I'm thinking that if Axaal is to be Rochefogne but with memory loss is because of Atamos. In XI Atamos has the power to eat false histories or time lines that would cause a paradox. It lives in the rift. During the main story of Wings of the Godess we see what those affects can lead to as it gets persuaded into eating the time line that would result in present day Vana'diel. People start forgetting one of the main npcs and how things actually unfolded during the crystal war. So that events would be remembered with how they played out in a parallel time line where the Shadow Lord won only to have Odin betray the Shadow Lord and become a heartless ruler over all of Vana'diel.
Now I could be wrong and that's fine. He could be just a nobody who happens to know Prishe and had a hand in defeating the Shadow Lord at some point in time. And yet why not use a guy who would have good reason to know Prishe, has the same hairstyle and is a sword and shield user. Many XI players wouldn't know of him as you only had to be rank 6 in order to start Rise of the Zilart missions and rank 5 story for all starting nations gave you an ending. I don't think you even had to start rank 6 mission. Just to be rank 6.