Yggdrasil, the world tree, is an immense ash tree that is central to the Asgardian dimension. The tree is supported by three roots that extended far into the other worlds; one to the spring of Hvergelmir in Niflheim, one to the well of Mimir in Jotunheim, and another to the well of Wyrd in Asgard.
In October 2014, a fourth volume of Thor debuted that featured a female character (later revealed to be Jane Foster) in the role of Thor after the classic hero is no longer able to wield Mjolnir. The writer, Jason Aaron, stated that "This is not She-Thor. This is not Lady Thor. This is not Thorita. This is Thor. This is the Thor of the Marvel Universe. But it's unlike any Thor we've ever seen before."