Symbolism, Imagery, Allegory
Invisible Ink
One of the first things we learn about Karou is that she has "bright blue hair [and] a constellation of tattoos" on her body. Ooh, pretty. Then we never hear of those tattoos again. Maybe because of their impermanence—Karou can just wish them away, unlike the rest of us—they have less meaning…?
Not all of her tattoos can be wished away, however. She's got permanent ones on her palms: the eye-shaped hamsas. And those are critical plot points. Whenever Karou is near Akiva she feels "the pulse in her palms that [...] emanated from her tattoos" (14.48).
This pulse could really mean all sorts of things. Lustful feelings are the first thought we had. But when we learn what the hamsas mean—they belong to chimaera who have been resurrected—they take on a whole new significance. They're protection against the seraphim.
But why would Brimstone give Karou hamsas when he knows that Akiva, a seraphim, is her one true love? That's exactly the kind of question we think you should be asking, Shmoopers.
So, to recap: tattoos are protection in this novel. But they also seem to imply foreboding, because why would one need extra defenses against one's lover's kindred? Stay tuned for the sequel, and all of your burning questions just might be answered.