Hitchcock employed the term "MacGuffin" as the mechanical element that crops up in any story, usually of no importance, simply driving the plot along, whereas George Lucas describes it as powerful, the audience caring about it as much as the heroes and villains.
I subscribe to the latter. JauntWorld, being essentially a sci-fi thriller, needs the strong MacGuffin to be the impetus for the plot to develop, and the protagonists and antagonists to struggle over.
The timebending alien jewels in Jaunt are more powerful than any technology humanity had yet developed, and of course are threaded throughout the story. How I invented these jewels are lost to the crooks and folds of my brain, but they were an early story device from the first sketches of what was then "Temporal Retrieve."
Ether needed its MacGuffin, and that is provided by the suitably mysterious property of spacetime termed "dark energy," its effects first described in 1998.
Until the MacGuffin decides to rear its head, there is no story, simple as that. Although, a kernel was recently planted for the finale....