Dark sorcery

Dark magic worked inside the bounds of the world and for evil ends. Those who practise it in Arda are almost always the Dark Lords themselves, Melkor first and Sauron after him, or servants they have taught. Morgoth used it in Utumno and in Angband, where he made and unmade creatures, and much of the marring of Arda came out of that work. The Sindarin word for it is morgul, which is why so many evil places, things and beings of the Third Age carry that syllable in the names by which they are commonly known.