So, Nova received that vision a long time ago. And ever since then, they only had sparse whispers from beyond...well, at least typically.
Hardmode Nova makes Nova more powerful by asking the simple question of what if they had a little bit more than sparse whispers? What if Nova was extremely linked to Creator, to the point of almost being more attatched to Infinity than the world around them? Nova's eyes are closed, but that one special wacky third eye of theirs? It's more open than ever before. And that has a lot of implications.

You thought they thought too much already? Try having them think about everything. That doesn't go over well with all the other Stars, though.