Fanged, clawed, and fond of dressing all in black, Jael is the last of the four alter-egos to appear in the novel, though it's she who has brought them together. Compared to the others, Jael is the living, breathing manifestation of Joanna's righteous anger. She's the dark dystopian counterpart to Janet's golden utopianism. And she's the backbone that Jeannine never had. She is frightening, deadly, and has a terrifying laugh. In essence, she's a parody of anti-feminist stereotypes about feminist women.
At forty-two years old, Jael is the oldest of the four J's, but not by much. Although her name sounds Kryptonian, it's actually from the Old Testament: in the Book of Judges, a woman named Jael defeats the captain of an enemy army by lulling him to sleep with a blanket and milk, then driving a tent peg through his head. That's the kind of ruthlessness that this Jael's got written all over her.
When Janet, Jeannine, and Joanna first meet her, Jael appears to be invisible, because her black clothing camouflages her in an apartment where the curtains and the furniture are black, too. Like Darkwing Duck, this lady slips in and out of the shadows like it's nobody's business. Her hair and eyes are silver, "her teeth seem to be one fused ribbon of steel" (8.2.5), and her fingers are strangely deformed. She "has hairpin-shaped scars under her ears, too" (8.3.1), but whereas Janet's scars come from the duels she's fought on Whileaway, Jael's come from the reconstructive surgery that has equipped her with fearsome combat skills and made it possible for her to pass, when necessary, as a member of the Manland police.
Jael works for Womanland's Bureau of Comparative Ethnology, the intelligence agency that keeps tabs on the Manland men. A cross between Jason Bourne, James Bond, and Glenn Close as Cruella de Vil, she's a force to be reckoned with.
As Janet, Jeannine, and Joanna learn, Jael has been tracking down other quantum versions of herself illegally. No one else in Womanland knows she's been helping herself to the probability travel technology, and few people know what her end-game is, either. What Jael wants is for there to be a final end to the decades-long war between the women and men of her world. It's been ages since there's been any real combat, and some of the women don't seem to be taking it seriously anymore. As Jael tells the others, some of them even think that they'll "win the men over by Love" (8.9.8).
Ultimately, Jael isn't interested in brokering truce. What she wants is a clear victory for the women, and she plans to get it by wiping the men off the face of her Earth (and others) for good. What she tells the other three J's is this:
We want bases on your worlds; we want raw materials if you've got them. We want places to recuperate and places to hide an army; we want places to store our machines. Above all, we want places to move from—bases that the other side doesn't know about. (8.15.8)
As Jael tells the other three J's, Womanlanders have already been using probability travel to infiltrate patriarchal societies on other worlds. Jael herself once spent a year and a half living "in a primitive patriarchy on an alternate Earth," one that looks a lot like courtly Britain, and is probably a playful nod to Edmund Spenser's The Faerie Queene:
With my silver hair, my silver eyes, and my skin artificially darkened to make me look even stranger to the savages, I was presented as a Prince of Faery, and in that character I lived in a dank stone castle with ghastly sanitary arrangements and worse beds for a year and a half. Jeannine must stop looking so skeptical—please reflect that some societies stylize their adult roles to such a degree that a giraffe could pass for a man, especially with seventeen layers of clothes on, and a barbarian prudery that keeps you from ever taking them off. (8.9.14)
As vicious as she is (when she needs or wants to be), Jael is also a great outlet for the novel's satirical humor. Take her favorite combat strategy: "The room is beginning to sway with the adrenalin I can pump into my bloodstream when I choose; this is called voluntary hysterical strength, and it is very, very useful, yes indeed" (8.8.81).
The joke here is that "hysteria" used to be a catch-all diagnosis for women who wouldn't behave properly. The "condition" pathologized any activities or desires that were deemed to be abnormal and chalked them all up to problems in women's uteruses. The history of the sham disorder would be kind of funny if it weren't for the fact that women diagnosed with hysteria were usually locked away in sanitariums or forced to undergo hysterectomies, and it's a grim reflection on the medical profession's historical treatment of women. Jael's lethal use of "voluntary hysterical strength" is another of the ways in which her character parodies misogynistic views (and treatment) of women.