Angra Mainyu (alt: Aŋra Mainiuu) is the Avestan-language name of Zoroastrianism's hypostasis of the "destructive spirit". The Middle Persian equivalent is Ahriman.
Read more about Angra Mainyu: In Zurvanite Zoroastrianism, In Zoroastrian Tradition, In Present-day Zoroastrianism, In Popular Culture