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SPOILER WARNING: Plot details follow. Caution is advised!
I wanted you to be proud of me. Out of everything that you taught me, killing was always what I was best at. It's ironic, isn't it? That that should be the reason you came to hate me.

–Jonathan to Valentine, Day of Atonement

Jonathan Christopher Morgenstern, also known as Sebastian, is the son of Valentine Morgenstern and Jocelyn Fairchild.


Early life

TMI202 Jonathan Christopher 01

Before he was born, Jonathan was injected with pure demon blood while still in Jocelyn's womb.[1] As a child, Jocelyn saw the destruction he was capable of and what she believed to be a natural inclination to bring death in him and slowly grew fearful of him.[2] After the Uprising, Valentine faked their deaths by setting fire to the Fairchild manor.[3] For years after finding out about his "death", his mother Jocelyn mourned for him. She kept a box of his things with her, and she would take it out once a year and cry over it.[4]

Valentine raised Jonathan secretly and in seclusion in a remote cabin in Idris, at the same time as, but separate from, Valentine's other experiment: Jonathan Herondale, whom Valentine was raising as Jonathan Wayland. Valentine kept journals of the two opposite Jonathans' progress. Jonathan claimed to have developed an interest in science as a child, after Valentine gave him a chemistry set and taught him the basic laws of physics.

Because of his demon blood, Jonathan grew up with murderous tendencies. When he turned eight, Valentine gave him his first seraph blade. He had been so eager to try it out and make his father proud that he snuck out of their cabin and killed and skinned a large werewolf, wanting to give its pelt to Valentine as a trophy.

TMI211 Young Jonathan02

At one point, a young Jonathan killed a boy named Albert Timberworth by throwing him off a bridge, apparently curious if the 32-foot fall would kill him. Jonathan's deadly experiments continued and began to attract unwanted attention, in addition to fearing that Jonathan was out of control and he could be his son's next victim, that Valentine eventually kept him shackled in the basement of the cabin. Eventually, he sent Jonathan to Hell, specifically the realm Edom. Jonathan felt that Valentine's reasons were that he grew to hate him for his inclination to kill and that his father chose Jace and wanted to protect him from Jonathan.

Time in Edom

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On Jonathan's first day in Hell, demons began to burn his skin—gradually, layer by layer—because he was too pretty, and too human, for their world. They made him hideous,[5] leaving his body disfigured, his face unrecognizable.[6] The demons also taught him how to use and draw power from his demon blood.

Jonathan spent his years in Hell clinging to memories and hopes of freedom. Eventually, he summoned the Greater Demon Azazel, who helped him escape Edom in exchange for his freedom from Duduael. Upon being freed, Jonathan found the cold unbearable, having gotten used to the flames of Hell. He was also disappointed to not have been overwhelmed with the emotions—anger, nor happiness—he'd expected to have when he finally made it back; instead, In the end, he felt nothing, though he eventually realized that he needed revenge on his father.[5]

As Sebastian

Jonathan spent time thinking of his next steps in his new life. To blend in,[5] Jonathan kidnapped the English Shadowhunter Sebastian Verlac from London and took on his identity. He led Sebastian's family believe that he was safe and just needed to be away.[7]

Meanwhile, Valentine convinced the other Jonathan—now known as Jace—that he was Jonathan Christopher Morgenstern,[3] until he was forced by the Soul-Sword to admit to him his deception. Meanwhile, a vision from Ithuriel told Jace and Clary that a "demonic Morgenstern" would be capable of destroying the Soul-Sword, denoting that someone like Jonathan would be able to do it. Because it was then believed that Jace was Jonathan, they wrongly assumed that it was referring to him, leading to him accidentally activating the sword. Clary was later able to deactivate the Sword,[8] and Jonathan, knowing that the Sword could be used to destroy him, a demon-blooded creature as well, stole the Sword with the intention of sending it to Edom with Valentine.

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Jonathan then had Azazel stage an attack on Isabelle Lightwood so he could swoop in and "save" her,[5] a deed which he hoped would later grant him access to the New York Institute. He took her back to his apartment. When she woke up, he offered her a vial of medicine that would help with her withdrawal symptoms. To gain her trust, he told her that he was also previously addicted to yin fen and found his own ways of kicking the addiction, one of them being the root extract medicine he was giving her. He convinced Isabelle to confine herself in his residence for at least a day to recover.[7]

After recovering, Isabelle invited Sebastian to the Institute, just as he had anticipated, where he proved his worth by imparting his expertise on Greater Demons and advising them how to defeat Azazel.[9] Jonathan was eventually able to gain the trust of the other Shadowhunters and integrated himself into the Institute, well enough that he became part of the team assigned to Valentine. He anonymously arranged for Luke to get access to Valentine's cell to kill him but reported him to Alec,[10] prompting Alec and the Clave to decide to have Valentine transferred to Idris to keep him safe, while he was being interrogated for the Mortal Instruments, from those who want him dead. This transfer gave him the opportunity to Portal Valentine away from the Shadowhunters through Duncan Armstrong, a Shadowhunter he'd been blackmailing into doing his bidding at the Institute. Jonathan had Duncan Portal them to the basement of the cabin he grew up in and later killed Duncan.[6]

Jonathan gave Valentine a recap of the life he had in Hell. When the remorseful Valentine took the blame for everything that happened to him and told Jonathan that he grew to regret sending him away, Jonathan refused to believe him and continued to prepare for the ritual that would send Valentine and the Soul-Sword to Edom. Valentine then took hold of the Sword and, compelled to tell the truth by the Sword, told Jonathan that he never hated him, that he had always and still cared for him despite his decision to send him away, and that he still thought of him and was haunted by his decision every day. He also told Jonathan that he was the "ultimate warrior" he'd always dreamed of, not Jace, and the man he'd grown up to be fulfilled this dream, calling him his greatest creation. This was able to convince Jonathan to change his mind, and he later took Valentine back to his place and had dinner with him.[5]

When Valentine left for Idris to summon Raziel, he left Jonathan behind in New York, claiming to have done it because of the danger. Jonathan decided to kill those in pursuit of them, for which Valentine Turned several mundanes to Forsaken to help him. Jonathan was able to take Jace by surprise and moved to hang him by the neck on a bridge, only to be coazed into a battle. While he bested Jace at first, Isabelle arrived and confronted him. He was distracted enough that Jace was able to stab him from behind. Jonathan tried to continue fighting, but Jace was able to kick him off the bridge and into the stream.[11]

In his dying moments, Jonathan crawled ashore and used his blood to open a rift to Edom and called for his "mother", Lilith. Through this rift, several asmodei entered the world, one of which took Jonathan's body and brought it to an isolated cave. The demons then coalesced into Lilith, and she was reunited with her "son".[12]

Personality and traits

Jonathan is an expert liar, able to blend in with others as a charming, compassionate, brilliant man. He also has masochistic tendencies, often burning his hand, due to his high resistance to pain after years of torture in Edom.

He is highly-educated and possesses unrivaled fighting abilities.

Physical appearance

Valentine Morgenstern: "Then why keep the Verlac boy's visage if you're weaker for it?"
Jonathan: "I think it rather suits me. Don't you? As does the accent. A bit more... charming than a demonic beast with burnt flesh."
―Jonathan about Sebastian Verlac's face, Day of Atonement

Jonathan as a boy had light blond hair. His eyes also sometimes turn completely black, particularly when he accesses his powers. After his time in hell, all the layers of skin on his entire body were burned off.

As Sebastian, he is tall and has blue eyes and blond hair. He has a "Calm Anger" rune on the left side of his neck.

Skills and abilities

  • Nephilim physiology: Being Nephilim, Jonathan should possess a variety of enhanced physical and mental abilities granted to him by the angel blood of Raziel in his veins and also by the angelic Marks of the Gray Book. This includes enhanced strength, speed, agility, stamina, and coordination, which continue to improve over time and practice.
    • The Sight: As a Shadowhunter, Jonathan should naturally and easily able to see through most magical illusions and layers of glamour over reality.
    • Runic magic: Due to the angel blood running in the veins of all Shadowhunters, Jonathan should be able to apply runes on his skin without any danger. These Marks would give varied effects that serve to benefit the wearer.
    • Use of heavenly weapons: As a Shadowhunter, Jonathan would also able to perform tasks unique to their species, such as the ability to use and call on the power of angels for their seraph blades, as well as to handle any heavenly weapons or objects with effect, which would normally not work for other species. In particular, these are tools made of adamas and forged by Iron Sisters.
  • Demonic blood empowerment: Being born with pure demon blood apparently gave him enhanced strength, speed, and others superior to those of normal Shadowhunters', as well as the ability to destroy small living beings, like a flower. According to Valentine, this would also affect his psyche.
  • Expert hand to hand combatant: Jonathan is highly skilled in armed combat.
  • Expert swordsman: Jonathan is highly skilled and proficient in swordsmanship.


Season One appearances: 0/13
The Mortal Cup:
The Descent Into Hell Isn't Easy:
Dead Man's Party:
Raising Hell:
Moo Shu to Go:
Alluded to only
Of Men and Angels:
Mentioned only
Major Arcana:
Bad Blood:
Rise Up:
This World Inverted:
Blood Calls To Blood:
Mentioned only
Morning Star:
Season Two appearances: 10/20
This Guilty Blood:
Mentioned only
A Door Into the Dark:
Flashback only
Parabatai Lost:
Day of Wrath:
Dust and Shadows:
Iron Sisters:
How Are Thou Fallen:
Love is a Devil:
Bound By Blood:
By the Light of Dawn:
Appears; eclipsed
Mea Maxima Culpa:
You Are Not Your Own:
Those of Demon Blood:
The Fair Folk:
A Problem of Memory:
Day of Atonement:
A Dark Reflection:
Awake, Arise, or...:
Hail and Farewell:
Beside Still Water:


  • He is portrayed by guest star Will Tudor, who also portrayed Sebastian Verlac. Elias Toufexis portrays Jonathan's true, charred form, and young Jonathan is played by Jacob Skiba.
  • The writers refer to him as "Bass".[13]

  • Listed below are characteristics or elements of the character in the books that differ from the show:
    • Jonathan was raised by Valentine until his teenage years and was part of his plans until the end.
    • Jonathan did not grow up in Edom, though he did spend his last moments there.
    • Jonathan did not appear burned and did not permanently take Sebastian's form. Instead, he only temporarily disguised himself as Sebastian by dyeing his hair black.