What fictional work does XXX exist in?
Yggdrasil
Yggdrasil (/ˈɪɡdrəsɪl/ or /ˈɪɡdrəzɪl/; from Old Norse Yggdrasill, pronounced (ˈyɡːˌdrasilː)) is an immense mythical tree that connects the nine worlds in Norse cosmology.