Steel Vigil Lore?

[GilbertLapine]

So, There two large watch towers on either side of Ishgard: the Stone Vigil (the dungeon), and the Steel Vigil (the place where Svara spawns). I get the Stone Vigil lore -- it fell after the chaos of the post-Calamity. What I can't find is the lore behind the gutted Steel Vigil.

When did the Steel Vigil fall? Was it to the Dravians or something else? What was its principle function?

[Malrend]

The only details that I've found, was that both the Stone and the Steel Vigils were under the care of House Haillenarte, and that even before the Stone Vigil fell to the Dravanians, the Steel Vigil had been abandoned for some reason or another (if you believe Lord Drillemont's accusations, then it was due to House Haillenarte's incompetence). This has been all that I have gleaned from what little information we're given during the story quests leading up to the Stone Vigil.