The "Nowhere" is in fact the Guf, ultimate source of all souls.
AKA, the spark of "something" that all sentient creatures possess, which also gives them the ability to feel and express emotion. Those who live in the Nowhere literally rely on memes to survive.
For Spensa, her obsession with heroic stories contributes in keeping her sanity intact. For the delvers, it was grief, loss, and hatred. In here, higher-level combat is fought with literal thought viruses.