"There is a hole...in your mind."
- – The Assassin to Sinclair
In 2257, as Babylon 5 neared its one year anniversary of going online, the Minbari Assassin was sent to the station with the intent to assassinate the incoming Vorlon ambassador, Kosh. He had been sent by his clan, the Wind Swords, to frame Jeffrey Sinclair for the murder, disrupting the new and still fragile peace of Babylon 5.
He was to meet Del Varner to buy a changeling net before arriving at the station but Varner was delayed. Instead he continued to travel on the Narn vessel and used a pod to burn through the station's hull. One aboard, he quickly tracked down Varner, killing him and using the net to assume his identity. The assassin was then able to take the form of Jeffrey Sinclair and poisoned the ambassador through a "patch" he applied to the Vorlon's hand.
When the station crew unearthed that someone had killed Varner and possessed the net, they were able to corner the assassin. Sinclair himself fought him, critically injuring him and proving his innocence at the same moment. Rather than surrender, the assassin activated a bomb on himself, after telling Sinclair that he had a "Hole in his mind." Sinclair managed to avoid the blast, with some help from Delenn, who apologized for the actions of the Wind Swords.
There has been no in-universe explanation as to why the assassin's bone crest is shaped like that of a female Minbari.