Erebus

Erebus is the Greek God of Darkness, (Ex) Patriarch of The House Of Erebus.
Husband of Nyx. Father of Apate, Momus, Morpheus, Icelus, Phantasos, Hypnos and others.
First appeared in Season 1, was the Big Bad for the first and second seasons, and died in Season 2. His ghostly spite-shadow re-emerged in Season 5.
==Season 1==
Erebus sent The Moirae to decide the fate of the infant Fionn Corvin whereby Lucifer slew two of the sisters and bathed the infant in their blood.
As a result of this Lucifer went to Erebus to plead for peace, asking that his child be left alone. Erebus agreed on the condition that Lucifer spend one thousand years in the pit of Tartarus with Sisyphus. Lucifer agreed.
Fionn Corvin as protector of Clearwater killed many of Erebus's agents and even his family.
==Season 2==
Erebus hatched a plan to open a portal to lead millions of damned soldiers to earth starting with Clearwater, and make everything in the image of Tartarus.
Erebus was obsessed with Fionn, wanting to turn him to the Darkness but also wanting to destroy him.
Fionn led The Squad to Tartarus to free Lucifer and prevent Erebus from invading Earth, this became known as The Tartarus War.
The war ended when Fionn killed Erebus, tearing his heart out and showing it to him for its final beats as he had long vowed he would.
Fionn fell in love with Apate, daughter of Erebus and they had a child, Ford Corvin.
==Season 5==