The Ten Great Primordials Main Villains

Mike, Camael and Zach will fight many things

Season 1 (Awakening)
Main Villain(s): Verchiel, Amen and Princes of Hell (Lucifuge, Beelzebub, Mammon, Leviethon, Aamon and Asmodeus)

Minor Villain(s): Powers, Demons and Raguel

Season 2 (Ancient Foes)
Main Villain(s): Samuel Beobachter and Lucion Iferiasm

Minor Villain(s): Gevallen, Duivels, Samyaza and Camael

Season 3 (Now, we're all falling appart)
Main Villain(s): Nachiel, Sorath and Ezekiel

Minor Villain(s): Angels and Demons

Season 4 (Monsters are here)
Main Villain(s): Typhon, Echidna and Primordial Beasts (Behemoth, Leviathan and Ziz)

Minor Villain(s): Alpha Monsters (Smaug, Vlad Tepes, Lycaon and Ithaqua), Firstborn Monsters (Cerberus, Ladon and Alphard) and Monsters

Season 5 (Apocalypse Now)
Main Villain(s): Lucifer, Damien Thorn and Morgoth

Minor Villain(s): Diablo, Smaug, Lilith, Horsemen (Tod, Hunger, Krieg and Krankheit), Fallen Angels, Demons

Season 6 (O' Death)
Main Villain(s): Necrosians (All-Death, Great-Death and Small-Death)

Minor Villain(s): Nyarlathotep, Children of the Barrow (Surgeon, Therapist, Anesthesist and Diagnostician) and Reapers

Season 7 (Rulers of Hell)
Main Villain(s): Archdemons (Mephistopheles, Baal and Diablo) and Imperius

Minor Villain(s): Greater Devils (Andariel, Duriel, Belial and Azmodan) and Demons

Season 8 (Eldritch Freedom)
Main Villain(s): Outer Gods (Azathoth, Nyog-Sothep, Nyarlathotep, Shub-Niggurath and Yog-Sothoth) and Amara

Minor Villain(s): Great Old Ones (Cthulhu, Hastur, Nyogtha, Ngyr-Korath, Mordiggian and Tsathoggua)

Season 9 (In Darkness, we find Light)
Main Villain(s): Sheol

Minor Villain(s): Amara, Archdemons (Mephistopheles, Baal and Diablo), Outer Gods (Azathoth, Nyog-Sothep, Nyarlathotep, Shub-Niggurath and Yog-Sothoth), Greater Devils (Andariel, Duriel, Belial and Azmodan) and Great Old Ones (Cthulhu, Hastur, Nyogtha, Ngyr-Korath, Mordiggian and Tsathoggua)