Setting up Sinclair? Kosh recognized Sinclair (actually the assassin, but close enough) as Valen right off. You'd think if he'd been in on the plan he would have aborted then and there.
This was discussed a year ago in another thread and I posted my theory. This is one I came up with just for fun to try and make sense of 'The Gathering'. I did write it as a proper article with the possiblity of getting it published. Think of it what you will.
Here is part of that article.
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During the season one episode ‘The War Prayer’, Sinclair asks at one point, how did Kosh get poisoned when his hand should have been completely covered by the encounter suit. That question has never actually been answered and once one question is raised, more follow. Such questions as why are the Vorlons so eager to take Sinclair back to the Vorlon Homeworld when previous expeditions have disappeared?; Does Lyta Alexander know Del Varner, as she is seen talking to him a number of times?; Why was it a Minbari and not a Narn that was the assassin?; How did Del Varner manage to get onto the station if he is wanted so badly by Earthforce?; etc.
After events in ‘Falling Toward Apotheosis’, matters are even more confused. If the true form of a Vorlon is that of a flying jellyfish, what did Dr. Kyle see in Kosh’s encounter suit?; and, If it took the combined efforts of Kosh, Sheridan and Lorien to kill Kosh2, was Kosh ever actually in danger of dying from the poison in the first place?
Answer: the Vorlons were behind it all.
B5 timings indicate that the Icarus reached Z’Ha’Dum late in 2256 and that The Gathering begins on 3rd January 2257. This would mean that Kosh knew about the Shadows’ return when he arrived at the station. Considering the Vorlon’s involvement with the Minbari during the previous Shadow war, it is likely that they also knew that Sinclair was destined to be Valen. It is plausible then that the entire assassination attempt was just an excuse to get Sinclair to the Vorlon Homeworld where he could be ‘programmed’ ready to be sent back in time to take on the role of the great Minbari leader. How else could a whole Vorlon fleet manage to reach the station within twelve hours when Kosh’s ship took almost a week, unless they had planned to be there.
The Vorlons planned the assassination, but they needed help from the other races. The Minbari at this time are their only allies so they are enlisted to provide the assassin. It is interesting to speculate that perhaps the Minbari chosen is actually a Ranger. The Rangers were around at the time, but only in a dormant role.
The assassin could not involve other Minbari, so approached the Narn, with a suitable explanation, to provide transport to B5 and help in procuring the changeling net. Del Varner is contacted to smuggle in the net, but as he is wanted on a number of counts of tech running, he will need help to get on the station. Contacts he has in organisations such as the Homeguard will arrange access through their B5 agent Lieutenant Commander Takashima.
It is common knowledge that Laurel Takashima was the original recipient of the Psi-Corps secondary personality and would have been involved in the assassination of the President, so it is safe to assume that she assisted in the Kosh assassination attempt. She would not be aware of the Vorlon involvement although it is likely that she was in contact with G’Kar. She could tell him of the early arrival of Kosh, though that was probably already known by the assassin, and would have halted the transport tube that delayed Sinclair.
At the time of the actual assassination attempt, the Minbari assassin is nowhere near the docking bay, which is why no one is detected going in or out. What happens is that Kosh enters the bay, looks around to see that he is alone, then poisons himself, knowing that he will come to no harm. He then sets off the alarm and plays dead for Garibaldi and Sinclair.
In Medlab, the Vorlons send a signal that the encounter suit is not to be opened. Perhaps they have covered every eventuality or they think they know Sinclair well enough to predict that he will go in anyway. Kosh is ready and projects the image of the angel to Dr. Kyle, which confirms the humanoid form of a Vorlon. He discovers the poison in Kosh’s system and from the Vorlon manipulated readings, estimates how much time he has left. During the examination, Kosh plants a suggestion within Dr. Kyle’s subconscious to have Lyta scan him to identify the assassin.
Dr. Kyle discusses the possibility of a scan with Takashima, who objects at first, but quickly gives in, as implicating Sinclair is all part of the plan. Lyta too seems to be almost too easily persuaded, but she begins the scan, Kosh’s encounter suit opening conveniently just when it is needed. She then sees what Kosh wants her to see; Sinclair poisoning Kosh. The fact that Lyta thinks it is a real scan and not a false memory is that the Vorlons have somehow already had contact with Lyta and programmed her, to respond in the correct way. Perhaps that is why she does not know the story of the first four Babylon stations, and also why she was seen talking to Del Varner/Minbari.
When it gets to the hearing, G’Kar does most of the talking as he knows the details of the official plan, including contacting the Vorlons although he is unaware that they are behind it all. At the vote, Delenn abstains because she knows what is going on and to say yes or no would be tantamount to a lie.
Del Varner’s body is then found, which might be the complication that G’Kar mentions to the assassin, or perhaps Takashima is threatening to expose them if she feels threatened. If this happens, the Vorlon involvement would become public, which cannot happen.
The second attempt on Kosh is therefore the assassin’s way of drawing all attention to himself so that the Vorlon involvement is kept secret. He is willing to die to ensure that the Vorlons’ intentions are not revealed until they are ready.
Right on cue, Takashima ‘discovers’ the changeling net information, saving herself and effectively clearing Sinclair, but scuppering the Vorlon plan. She is also the one that suggests the recorder and transmitting the signal to the Vorlons. All that the fleet can do is play along and watch as the Minbari fights Sinclair and sacrifices himself.
All that remains then is the clearing of the debris. Delenn provides information that neatly explains why the assassin was Minbari, and the counter agent to the poison works better than hoped in restoring Kosh to full health.
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Clear?