Ginna Jar is the ghost of something important that has been lost and is gone. The Orlanthi give it a feminine identity, but that may have as much to do with the sleeping Earth goddess before the Sacred Time as anything else.
In short she’s a mystery element in the ceremony. If WE mortals are Flesh Man, Ginna Jar is our lost dreams, love and hopes.
Who is equivalent figure to Ginna Jar in solar mythology (Dara Happan or Pentan)? Where did the scattered bands in Peloria put their lost dreams, loves, and hopes? That’s where you will find Ginna Jar. Or it is called She Who Waits.
The other way of thinking about this is that Yelm was already hanging out with Ginna Jar in the Underworld. While Emperor of the Dead, he was surrounded by lost dreams, loves, and hopes.
Here’s something else: Glorantha, Ginna Jar, and Arachne Solara are all the same being. Greg was clear on that mystery.