Who's This? The Monitor's messenger.
The facts: First appearing in New Teen Titans Annual #2 (1983) as an orphan girl raised by the Monitor and serving as his assistant, Lyla Michaels put in many appearances preparing us for the Crisis on Infinite Earths (or whatever - creators Marv Wolfman and George Perez famously didn't know what the Monitor would end up doing). When the Crisis was triggered (CoIE #1, April 1985), she was transformed by those big honking tuning forks into a "multiple-copy person" named Harbinger, and sent across time and dimensions to recruit the heroes to fight the Anti-Monitor and his forces. At the end of DC's mega crossover event, she's the one who puts the History of the DC Universe package together, then is only rarely seen. During War of the Gods, she's seen working with the Amazons as their historian. She sacrifices her life to save Supergirl in Superman/Batman #9-10 (2004) and returned as a Black Lantern during Blackest Night. An A.I. who identifies as Harbinger appears in The Multiversity.
How you could have heard of her: The Flash and Arrow TV shows have a Lyla Michaels who is an agent of ARGUS and Diggle's estranged wife (she does secretly work for the TV version of the Monitor).
Example story: Crisis on Infinite Earths #6 (September 1985) "3 Earths! 3 Deaths!" by Marv Wolfman, George Perez and Jerry Ordway
So I'll spare you 5 issues of Harbinger recruited superheroes and villains to the cause and get to her most heroic moment. At the start of Crisis #6, the Monitor's satellite HQ is under attack and she is present. This place has been her home for a while, and her father figure is dead at one of her duplicates' hands (all part of the Monitor's plan, but she doesn't know that). So this is a moment of personal crisis that activates her as a heroine.
It's Crisis-specific characters arguing about which one should die, so perhaps a bit "whatever", but if the visuals are going to be this gorgeous, you're not going to hear any complaint from me. So what's happening? Well, Earth-1 and Earth-2 have already been brought into a "Netherverse" where they'll be safe from the Anti-Monitor's forces, and three more surviving Earths (X, S and 4) are in the queue. If only the satellite can generate enough energy before it explodes. Don't ask me what the physics are play are, exactly, but Harbinger manages it by flying into her original self at the center of a mechanical womb.
Maybe it's paradox energy, I have no clue, but it works. We think her destroyed, but no, she's taken on all these energies and, like a goddess, saves the five worlds by merging their histories together!
Looks like more than five, but I like to think there are small details from other Earths included. Or perhaps they're finally being honest about the Multiverse and saying it's not just Earth - there's a whole universe of planets that are also merged with one another. Either way, this expenditure saps Harbinger of her power and she turns back into Lyla.
You know, she dresses like the Time Trapper. I'm surprised she's never been the villain at the end of history. She'll turn back into Harbinger after a few more issues, don't worry, and be on tap to record the almost-immediately outdated History of the DCU. Not that we really need a Harbinger beyond that. This is a character that was intimately tied to a specific event, and more than that, to a specific character specific to that event. With the Monitor dead, what's Harbinger to do? Show up every "crisis" to assemble heroes? What a lame destiny.
That said, there could have been opportunities. Once the Multiverse was restored and we had a bunch of Monitors, each could have had a duplicate serving them, with each different because of the Earth's specific "vibration". An evil Harbinger of Earth-C, a pirate Harbinger of Earth-494, etc. Maybe there was something there, who knows.
Who's Next? Green Lantern's second wife.
Comments
it contradix canon and in general don't make sanse: well I can see supergirl and harvenger being defined by the furies it's weird that this battle whent so bad that She actually died specially nowing that She new it was coming.
it isn't clever as it thinks it is: Oh! big surprise the bloom woman that was killed on the vision turns out to be Laila not Kara? I didn't see it coming. I mean the Just supergirl after a few years of my fake starts and We have a character we haven't seen much of in a few years and no rider really care that much about. so don't see it coming.
it's more burning than the not twist option: picture this a world where havinger was present for infinity crysis She actually was a friend of Alexander Luthor and earth two Superman so She differently have more interesting perspective than Kara si probably have been and interesting new heat monitor sustitude in multiversity maybe becoming a new defender of the multiverse for every scholarship event not necessary and to recruit other heroes but She should be yours in more monitor related adventures(but they look at you that darkside field particularly yes serious that day plus everytime DC has considered opportunity of using havenger the More than like he would use kara in his place so).
it has no mean impact on the plot: do you guys not is that no One actually care about Lailas dead yes they do more her for like 5 minutes and then they continue plot. alex didn't care and no One else care they didn't care so much that She stay dead Paria and monitor return to life but Lila no she stay dead