Umëarauko

Umëaraukor were great creatures of pure Shadow, akin to Balrogs, but lesser than them. They were clothed in Unlight, a substance that was first used to make cloaks to hide Melkor and Ungoliant when they attacked the Two Trees of Valinor.

Etymology and Appearance
The name Umëarauko was Quenya for "evil demon". The Umëaraukor were huge, and a typical one was eight feet at least. They were similar to Balrogs in their overall appearance, but as a Balrog was shadow and flame, an Umëarauko was shadow. Their "shadow" was actually Unlight, a dark force that was simply a veil of complete and utter darkness.

History
Antiuca slew an Umëarauko in Minas Tirith by driving the spike of his helm into its heart, but he was rendered unconscious by the Unlight. Eäryéndë Greenleaf healed him.