The concept of time was born when Arthur traveled to the past, exactly when the Twelve just came into existence. His appearance changed many things and allowed them to distinguish themselves using magic or names. He taught many things, beginning from energy to magic to creation, which they learned quickly and perfectly.
At that time, Bilgart, also known as the Watcher, was present and he, too, was fascinated by the things Arthur said. He was born before the Twelve but his knowledge was limited due to his age, which didn't increase as there was no concept of time before the parasite's arrival.
He watched from afar and mastered everything Arthur talked about, be it the dreadful Shadow Magic or the laws of space, which allow you to teleport and even mess with the space-time continuum. He also learned that there are many things that can threaten him, like the Time Wraiths, for example, which are remnants of past victims who succumbed to the punishment of the Time Laws.