I think with world building, it's important to create a sense of culture even if it is just a fantasy, and the best way to do that is to look at a real human culture and see what makes it cohesive.
Laini TaylorAs far back as she could remember, a phantom life had mocked her with its impenetrable โsomething else,โ but now it was the opposite. Here, in the circle of Akiva's presence, even as they spoke of war and siege and enduring enmity, she felt herself being drawn into the warm absoluteness and rightness of him, like he was both place and person and, contrary to all reason, exactly where she was supposed to be.
Laini TaylorOnce upon a time, the sky knew the weight of angel armies on the move, and the wind blew infernal with the fire of their wings.
Laini TaylorOne world on its own is a strange enough seethe of coiling, unknowable veins of intention and chance, but two? Where two worlds mingle breath through rips in the sky, the strange becomes stranger, and many things may come to pass that few imaginations could encompass.
Laini Taylor