Valhalla is the afterlife where Asgardians go after death. Contrary to popular belief, I have not seen any evidence that Odin controls this place, in the film Thor Ragnarok we see Thor praying for Odin to be taken to Valhalla after his death. This shows that Valhalla existed before Odin, so who rules it and who did Thor pray to at that time? So I don't think Odin can send dead people back to Earth, what do you think?