The flow of time and space, the changes of the universe.
A year before the Dark Portal opened—Lordaeron:
Arthas struggled to climb up from the ground, and his memory was incredibly chaotic. He vaguely remembered that he seemed to be riding a horse, then falling, and then—no! He was clearly at the Genesis Sanctuary battling with the allied forces, his brother said something strange, then the memory became somewhat blurry—what exactly happened?
Arthas rubbed his head, the pain in his body was exceptionally clear, but the sound of a horse's neigh made him turn around. He found his beloved horse 'Invincible' lying on the grass, whimpering in pain.
He instantly remembered the time when this scene occurred—it was the year he was seven, he was riding 'Invincible' galloping in the wild, and during a leap over a ditch, he accidentally fell off the horse. 'Invincible' also died in that incident, it was his first time witnessing death, leaving an indelible shadow in his heart.
