The decree you found made mention of a plan to defeat the Old Gods.
I know that the Amathet aren't likely to work with us toward that goal, but if they have a plan tae take out N'Zoth, it's worthwhile for us tae look at it.
The decree mentions the Engine of Ascension. I think that might be what they call that solar empowering device we saw earlier. We should take a peek underneath and see if we can figure out what they're planning!