The Assassination of Ulkesh was a plot devised by John Sheridan to eliminate Ulkesh Naranek, ambassador of the Vorlon Empire to Babylon 5. Following the destruction of three planets deemed by the Vorlon to have been influenced by the Shadows, Ulkesh was confronted at his quarters by Michael Garibaldi and Babylon 5 security. Garibaldi demanded the Vorlon to leave the station due to his governments' actions. Ulkesh attacked and forced the humans to leave his quarters.
Afterwards, Lyta Alexander came to warn Ulkesh that Sheridan would make a move against him and that there was a human with a piece of Kosh inside him. Angered at the thought of a human imprisoning a Vorlon, Ulkesh followed Lyta outside to the central corridor in Blue 24. Ulkesh, suspicious of Lyta's troubled thoughts turned on her, but it was too late for him, he had fallen into the trap. Blased by an electrical field and shot by security guards, the headpiece of Ulkesh's encounter suit shattered.
Enraged, Ulkesh emerged from the encounter suit and faced his attackers, while his personal transport broke away from the station. After turning to Sheridan, the piece of Kosh that had remained inside Sheridan since his death emerged to confront Ulkesh. The two incorporeal shapes fought throughout the station, all the way to Ulkesh's ship, which then exploded.
With Ulkesh gone, Sheridan's plan to face both the Shadows and the Vorlon was safe.