From "Babylon 5: Ceremonies of Light and Dark (#3.11)"
[Londo Mollari asks Lord Refa to sever his relationship with the Shadows
Oh Londo, you are a fool. You walked away from the greatest power I have ever seen. Now you expect me to do the same? They are the key to my eventual rise to the throne! Why would I abandon them?
Because I have asked you. Because your loyalty to our people should be greater than your ambition. And because I have poisoned your drink.