Okay, Ibelieve ran out of room last time but that is why we make part two's

Anyways, the golden apple rolls over towards Nightmare and he accidentally touches it, causing it to turn black, and then he eats the apple thinking that there is no other way and then he becomes goopy, avenges his mother Nim by unaliving all the villager and then Dream is overwhelmed by the negativity and gets turned to stone and that is the real story to Nootmares backstory