Dawn Of The Machine Question

Hey,

so yesterday I've completed my first playtrough of the new expansion.

Really AMAZING stuff.

However I'm now in the hub world and a bit confused, after getting the first rune.

Do I need to just play the single chapters again, to find the other runes, or are they all hidden behind secrets now?

And also, can I activate the Bloody Nightmare skill yet, when replaying the maps? Or is it something, I should have a lready gotten urgently in the first run?