Though possibly because of a misspelling, Svarthalfheim appears in one issue of Lucifer, during The Wolf Beneath the Tree story arc when Lucifer brings Michael, Elaine and The Host to that place, telling them it is the location from which Yggdrasil, the World Tree, expects to be approached, thus making their journey their "easier".
Svartalfheim is one of the Nine Worlds in Marvel's version of the Norse cosmos. The geography and climate of the realm has been shown to be heavily wooded with Dark Elf towns and castles doting across the landscape. Large caverns exist beneath the land that the Elves frequently inhabit. It is inhabited by Dark Elves who perhaps bear some kind of relationship with the Light Elves of Alfheim and the Elves found in the Otherworld of Celtic mythology. The Dark Elves have generally been hostile to the inhabitants of the other world and under different leaders embarked on schemes of conquest several times.
Dark Elves are about human in shape and size, but are distinguished by far longer life spans, pointed ears, and blue skin. Physically, the Dark Elves are superior to normal humans, but weaker than an Asgardian god. They can see in the dark. They have been shown to live both above ground in castles and underground in large caverns. The Dark Elves have their own portals that grants them access to Earth independent of Bifrost.
The government and culture of Dark Elves is along the lines of Middle Age Europe with different Elf lords ruling the land. The past ruler has been Malekith the Accursed. His often waged war against Asgard and allied with dangerous creatures like Surtur. The current ruler is Queen Alflyse of the Eastern Spires. She too has had plans of conquest, but generally cares more for her people than Malekith and tries to avoid the suffering he caused.
Dark Elves and their magic have a severe weakness to anything iron. Iron can cut through their armor and negate their magic. Dark Elf magic cannot directly effect anything made of iron.