Silk is a strange person that Childe met when he was young and strayed into the abyss. She taught childe many skills, and being in the abyss will slow down time. Three days outside is equivalent to three months in the abyss.
In addition, there are other NPC figures in Genshin Impact, such as Paimeng.
I hope the above information is helpful to you. For more information, please consult the official customer service of the game or inquire in the relevant game community.