WELP! "The Sun is a Phoenix" is certainly not the answer he was expecting, but it does explain a good deal and at least it's a lot more natural cycle than the one that his world is facing! Ignis will be glad of that.

He will be very thankful for their offered assistance, though also will stress he hopes they never have to see the mess that is to become of his world, if for no other reason that he is hoping to find someway to keep things from going so badly.

Ignis isn't going to properly be able to thank them for introducing him to the warriors, though at some point he will find a way to ask them--probably rather shyly (he might just be a little awed by how well they do without sight)--if they have any tips or advice for one who is attempting to relearn how to live and fight without sight.