I will raise up the dead, and they will devour the living,
I will make the dead outnumber the living!
(trans. Jeffrey H. Tagay)
These two lines are heralded as the world's first "zombie apocalypse," but this is only true if one takes them out of context and applies a hefty dose of imagination.
The lines in question were adapted for the Gilgamesh epic from an older poem, known as Nergal and Ereshkigal (5.11-12, and again at 26-27), where it is found verbatim, spoken by Ereshkigal, the Queen of the Dead, as a curse. The Mesopotamian dead, however, were not zombie corpses but rather, as the Gilgamesh epic (tablet XII) shows, as cold, lonely souls imagined as dust-eating birds:
[I was taken] to the house, whose inhabitants are deprived of light;
to the place where dust is their sustenance, their food clay.
They are clothed, like a bird, with feathered raiment.
Further, we know from Mesopotamian spell tablets that they believed in ghosts and feared risen spirits, implying that the dead were believed to take spiritual, not corporeal form. Thus, the released dead of Gilgamesh 6.99-100 and Ereshkigal 5.11-12 are ravenous ghosts, not actual bodies, who will consume the living. At any rate, this was a mere threat, never enacted, though interestingly in another poem about Inanna's descent into the underworld, demons from the underworld do rise to rend and tear her lover Dumuzi to shreds and drag his soul underground.