Astarion has a couple of lines, that I haven't heard on my playthroughs so far:
'Trading some whelp we've just met for impossible power? It's a fine deal.'
'You are the one dividing us!'
mentions 'prophecy of people falling from the sky' and aluando as well (just like the other companions)
He also says that we shouldn't weep over the deal, but that we should embrace the power.
This might be only related to him, but he seems to be haunted or something, from the Book of Thay possibly?

“There is only one thing we say to Death:
Not today.”