babylon 5 - How would anybody know how to poison a Vorlon?

The Vorlons in the Babylon 5 saga are very secretive. As far as we know, only two humans ever visited their empire and lived.

Vorlon territory was restricted to other alien species and (almost) every known expedition into Vorlon space failed to return to their respective governments. Much like the Shadow homeworld, Vorlon is protected by an array of highly advanced and automated defense systems designed to keep out intruders and primitive spacefaring races. These defense systems remain in place and active even after the Vorlons abandoned their home and left known space; evidence suggests that the systems will not allow outsiders entry to Vorlon until 1,000,000 human years have elapsed.

They wear encounter suits and very rarely leave the suits because they don't want others to see how Vorlons appear.

Despite their secretiveness about their empire, their history, and especially their physiology, somebody poisoned the Vorlon ambassador to Babylon-5. How would anybody know how to poison a Vorlon?

In the pilot episode, The Gathering, ...

a member of the Wind Swords, a militant section of the Minbari warrior caste, disguised himself as station Commander Jeffrey Sinclair, and attempted to assassinate Ambassador Kosh with poison.

A person could not pick a chemical at random and hope it works. If they tried sodium-cyanide, they might discover it just makes Vorlons hallucinate, but does not injure them. Or if somebody tried, potassium-chloride, they might discover that Vorlons use that the way we use table salt, sodium-chloride.

Later in the episode ...

Doctor Benjamin Kyle decided to risk treating Kosh, which meant opening the encounter suit. Determining that a cure would be impossible without knowing where the poison entered the Vorlon, Dr. Kyle convinced newly arrived Psi Corps telepath Lyta Alexander to scan the Vorlon. Despite the very strict Psi Corps rules in such cases, Lyta performed the scan.

So we have a separate, but related question of how could a doctor know how to treat a Vorlon for poison if he doesn't understand Vorlon physiology, which poison was used, or the effect of the poison on the body? While this second question is intriguing, it's not the focus of this post.

I prefer answers backed by canon sources; such as comments from the producers, novelizations, or screenplays.

Answer

Sinclair wondered this too, but never got an answer

In "The War Prayer", Sinclair wondered how someone could possibly administer a poison on a Vorlon. And not just what kind of poison, but to know the means of poisoning his hand while it was in a suit.

Sinclair: [The Minbari assassin] used poison, administered through the hand. I was talking with Kosh earlier and I remembered something I never could quite figure out. Kosh wears an encounter suit to protect him from our atmosphere, so how did the poison get into his system? His hand should have been completely covered.

Ivanova: Vorlons are very secretive. They don't want anyone to know what they look like, what they breathe, or how their biology works. I mean, who knows how much that suit is really necessary and how much is just…camouflage to keep us from seeing what's inside.

Sinclair: The only person who does know is Dr. Ben Kyle, who saved Kosh's life. Since he's bound by a doctor's oath of confidentiality, he never told me what he saw when he opened that encounter suit.

By "person", Sinclair really means "human" (although at this point, Sinclair was probably unaware of the Vorlon's connection to the Minbari). Unfortunately, this is something that he never got an answer to. The only two people who could provide evidence, Dr. Kyle and Lyta Alexander were transferred off the station. By the time Lyta returned, so much time had passed that she didn't feel the need to talk about it.

Remember though that this was a Minbari assassin and that the Minbari have worked with the Vorlons for a long time. It's not outside the realm of possibility that in the thousand years they've worked with together that they may have learned how to poison a Vorlon. Unfortunately, we see things from a human perspective and were never shown this aspect of Minbari culture.