Kara is the protagonist of this novel. Her full name is Kara Zor-El, and she comes from Krypton. She arrived on Earth eighteen thousand years before recorded history.
She is neither the hot-tempered big sister and alternate-universe counterpart from the comics, nor the pretty teenage girl from the animated series, and certainly not the disgrace of Krypton from the TV series who would have used humanity to repopulate Krypton if the villains had not had their own code of honor.
Her titles include the Terminator of the Stone Age, Mother of Humanity, Goddess of Wisdom and War, Time Traveler, Schrodinger's 404... and many others. The one title she never gets is Superhero.
In general, to make a story about an almost invincible protagonist work, you need to keep it engaging. Usually, that means giving the protagonist equally powerful opponents, shifting the main point of view away from the protagonist, making it so the protagonist's invincibility cannot change the world around them, or imposing various limits on them (kindness, stupidity, weaknesses). Or you can make the protagonist a jokester, a caretaker, a doting dad, and so on.
Over her long life, Kara gradually came to understand why powerful characters so often get taken out with such ease...
P.S. Not counting smut, not a single novel starring Kara has ever been completed online. Why does that sound so familiar?
