He is portrayed by Ian Tracey.
Ishim was the commander of a flight of angels consisting of himself, Benjamin, Mirabel, Castiel and two other angels. During Lily Sunder's study into angels, she discovered a spell to summon one and ended up summoning Ishim. Ishim became obsessed with Lily who he believed he fell in love with and shared with her all of the angels secrets for her research. Eventually, Lily began to fear Ishim and married the angel Akobel for protection.
Feeling that Lily left him for Akobel and desiring revenge, Ishim called upon his flight to get revenge, claiming that Lily's daughter May was a Nephilim she had conceived with Akobel. The angels confronted Akobel and killed him, then Ishim went into the house alone, claiming to want to kill the Nephilim by himself. Instead, Ishim confronted Lily about her leaving him and murdered May as punishment. Ishim would later claim he spared Lily out of mercy and that he cut out his humanity when he murdered May.
Like all angels, Ishim was affected by the Fall and lost his wings and ability to teleport. Ishim also grew to have a dim view of Castiel because of the sacrifices other angels were forced to endure for Castiel's .
In the years following the Fall, two angels from Ishim's flight are murdered by Lily Sunder who seeks revenge using the Enochian magic her studies taught her. Ishim decides not to tell Castiel, believing that he wouldn't care. However, after Lily murders Benjamin in 2017, Ishim calls a meeting with Castiel in a diner where he and Mirabel inform Castiel of the situation. Ishim is disgusted when Sam and Dean Winchester show up, having a dim view of humanity. Ishim sends Mirabel to check the perimeter and expresses his disgust with how far Castiel has fallen before ordering him to leave the Winchesters and meet him at a nearby safe house.
Outside, Ishim finds Mirabel dead and is attacked by Lily who scores a deep angel blade wound in Ishim's side. Ishim attempts to smite Lily, but she is immune and tells Ishim that she is not as powerless as she once was. Ishim and Lily fight before Castiel arrives and wounds Lily. When the Winchesters intervene, Lily blinds everyone with a blast of white light and escapes.
Retreating to Ishim's safe house in a nearby church, Ishim is unable to heal his wound and refuses Castiel's offer of healing. Despite Ishim telling Castiel that he doesn't owe the Winchesters any explanation, Castiel tells them what he believes happened the day of Akobel's murder. Ishim explains who Lily is and claims she made a demonic pact for her immortality and powers. Ishim watches as the Winchesters argue with Castiel over trying to talk Lily out of her revenge instead of killing her and concurs with Castiel's that it won't work, knowing the true reason Lily wants revenge.
As Castiel heals Ishim's injury, Ishim tells him that the truth is, angels aren't dangerous to humans, humans are dangerous to angels. Castiel is able to heal Ishim, but doing so leaves him weak while Ishim feels better than he has in a millennium. Ishim is amused when Castiel can't find his cell phone and promises that Castiel will soon feel better.
A short time later, Dean returns and tells Castiel the truth about what Ishim did, having found out from Lily. Castiel confronts Ishim who attempts to lie, claiming that Lily had been lying as she's human. Dean sees through Ishim's lies while Castiel realizes that Dean is right since his words are bothering Ishim so much. Ishim finally admits that Dean is right and as he advances on Castiel, Dean draws an angel blade and attempts to attack Ishim who telekinetically throws Dean into a wall. Ishim then beats on the weakened Castiel who is no match for him, taunting that he once envied Castiel and will cure him of his humanity by cutting it out. Drawing an angel blade, Ishim turns his attention to Dean who has drawn an angel banishing sigil on the wall and threatens to activate it. However, Ishim warns Dean that in his weakened state, Castiel will likely not survive a banishing and Dean backs down.
At that moment, Lily and Sam arrive, armed with angel blades and Lily and Ishim engage in battle. Dean and Sam attempt to help Lily, injuring Ishim in the arm and leg, but he easily defeats them. Lily then uses her Enochian magic to pin Ishim to a wall, but he tells Lily "you can't hold me forever", pushes through it and advances on Lily. As Ishim goes to kill Lily, Castiel stabs him through the back with his angel blade, killing Ishim. Castiel then tells Lily she held Ishim for long enough.
Following Ishim's death, Lily stands over his body and the imprint of Ishim's broken wings burned into the floor of the church. The Winchesters question whether or not Ishim dying will be enough to satisfy Lily, but she isn't sure as revenge is all she's had for over a hundred years.