To read more about Phantom’s character and origins go here: The Phantom
Origin

In the lineage of The Phantom, it is not only the son who becomes the Phantom. Sometimes a lady in the lineage would also take on the task of the Phantom in a similar Phantom outfit. The centuries old Phantom chronicles has a mention of a female Phantom, Julie Walker.
Sometime in the 19th century, the 16th Phantom, ancestor of the current 21st Phantom (21st Century) had twins, a boy and a girl. The Boy, Kit Walker became the 17th Phantom, of course. But once when he became ill, Julie took his place to maintain peace and order in the jungles of Bengalla.
Creation
In 1969, Julie Walker was created by Lee Falk, creator of The Phantom. She was the only female Phantom mentioned by the author. Although Lee Falk created Julie Walker, many other authors have also written stories about how she was brave and intelligent taking on the role.
Character Evolution
As depicted in many stories, she has a pet Fury, a Cheetah and her horse is named Flash. With the help of Fury and Flash she is found to have faced many threats in the jungle and also have protected the hundreds of years old Phantom secrets and treasure from the thugs who tried to break into Skull Cave.

Meru is Julie’s native companion from the Pygmy tribe who helps her in her adventures. Once she has saved Julie’s life as well from a witch who was bent upon killing the ghost who walks.
Her role as the Phantom is very short and ends as soon as her brother Kit, the original Phantom at that time, gets well.