The fel elves are a group of Kael'Thas Sunstriders's most trusted followers. They were given this "gift" by Man'ari eredar, Kil'Jaeden which allowed them to fill themselves with felblood, a demon blood type. Some stay in the Outland, others went with Kael'Thas to Azeroth. Fel elf recruits remain in the Outland at Kil'Jaeden's throne, where they siphon upon fel energy. Selin Fireheart is the only well known felblood elf, he captured M'uru the naaru. Selin Fireheart placed him in the secret blood knight chamber. When not wearing clothes, on their faces you can see pure fel energy flowing through themselves. They also have runic tattoos on their body.