Wow, I don't remember any of this.
I just started re-reading the first Psi-Corps book, as I'm planning to re-read all the books in chronological order, more or less, jumping between trilogies.
All? Dell 1 thru 9, the three novelizations and the three Del Rey trilogies? ...or just the following?
Babylon 5 Book #7 - The Shadow Within (11/2256 - 01/2257)
Babylon 5 Book #9 - To Dream in the City of Sorrows (Marcus in 10/2260, recalling events of 1/2259-9/2260)
Dark Genesis - The Birth of the Psi Corps (2115-2189)
Deadly Relations - Bester Ascendant (2189-2258)
Final Reckoning - The Fate of Bester (2271-2281)
Legions of Fire - Book I - The Long Night of Centauri Prime (2262-2266)
Legions of Fire - Book II - Armies of Light and Dark (2266-2273)
Legions of Fire - Book III - Out of the Darkness (2274-2278)
The Passing of the Techno-Mages - Book I - Casting Shadows (11/2258-12/31/2258)
The Passing of the Techno-Mages - Book II - Summoning Light (1/2259-2/2259)
The Passing of the Techno-Mages - Book III - Invoking Darkness (8/2260-2261)
In the Beginning (Londo in 2278, recalling events of 2245-2247)
A Call to Arms - 12/2266-1/2267
Thirdspace - 5/2261
I still haven't read Shadow Within.
You should read "The Shadow Within" immediately before the first book of the Technomage trilogy ("Casting Shadows").