On NG after completing the true ending. Trying to see how much I can break or change but it turns out even though you can kill any npc there is no changing the story or working around anything. As soon as I meet >! Ambrosius !< I kill him and the only thing the oracle says is to revive him. I'd already killed the dragon forged and same thing. Why even make them killable if all it does it waste a wakestone? Maybe my hopes were too high but I was really expecting something to happen after I found ways to skip to melve without the escort mission or resting at the inn. NG is pretty useless if there's no choices to be made and being level 50 means all the fights are a breeze.

Edit: just started the oxcart quest again. Turns out you can't hit any of the npcs related to that quest when they first show up. You just phase through them so clearly some npcs are invincible for quest purposes.