Svartalfheim is the realm of the Svartalfar, a strange and twisted realm of shadows. The sky is permanently shrouded by dark clouds. Often, giant floating continent further blot it further. No one knows if there is a proper sky or sun. What little vegetation exist is twisted and monstrous.
Dark, scary tunnels connect this realm to other subterranean realms, including Nidavellir and the material world.