Sebastien

Appearance
Sebastien, or Sebastian, or... Jonathan Morgenstern was a Shadowhunter born with demon blood. Sebastien had blond hair, and green eyes. However, when he appeared he had dyed black hair, and black eyes.

Magic
Sebastien possesed exceptional skills with magic, and was able to match skills with Magnus. Sebastien however, due to his brief appearance was not able to demonstrate much else.

In the RP
Sebastien appears when Magnus is revealed to have the ring that can bring destruction to the world. Sebastien enages in a fight with Magnus and Max when he escapes before he is defeated.

Sebastien does not appear again but Max kills him and takes the band.

Max
Magnus (indirectly caused)

Magnus was the one who introduced Sebastien to Max.

Max was the one to travel to the deep recesses of his homeland to find and kill Sebastien

Background
Sebastien was born to the Morgansterns and was born a demon.

Killed Victims
Magnus Bane (indirectly caused)

Trivia

 * Sebastien was one of the shortest living characters. He was only in The Silver Band, and he only made one appearance within that story.
 * However, he is only presumed dead which means there is a chance, albeit small, that he may return.
 * Sebastien was never shown to have died on-screen, but the wiki lists him as deceased