Some fans of the show -- who seem determined to inflate the abilities of the First Ones beyond anything the writer ever considered -- have used a few lines from the B5 novel Armies of Light and Dark to back their claims that the Shadows were capable of constructing their enormous, planet-killing "Death Clouds" at astronomical speeds, some going so far as to claim that the Shadows could complete a Death Cloud -- from start to finish -- in a matter of minutes. To address these extraordinary claims, we're going to look at the excerpts from the novel that over-eager fans use to support them.
There was some sort of activity at the far end of Xha'dam, and Vir tried to figure out what it was. The Drakh ships had reappeared, and had converged there. To Vir's confusion there seemed to be some sort of planet there as well. But something didn't....
Then he realized. "Great Maker," he breathed. "That's... not a planet."
"Its a Death Cloud," said Kane.
"A what?"
"A Death Cloud. Theoretically, it envelops a world and rains destruction down on it."
"Like a... a mass-driver or some thing?"
"A Death Cloud is similar to a mass driver," Finian said, "in the way that an adult with heavy artillery is similar to an infant with a toy hammer."
The comparison was horrific. Londo had been present when mass drivers had been used on the Narn homeworld, and the description he had given had been so ghastly that Vir had wondered about the minds of the people who had come up with such a weapon. Now, upon witnessing something that was infinitely worse, Vir thought of the Shadow creatures, and knew that they were more than mere alien beings. The Shadows were incarnations of all the darkest and worst impulses that the mind of sentient beings had to offer.
"You said ‘theoretically’, " said Vir. "You mean it was never actually used..."
"Our understanding was that it was close to completion when the Shadow War actually ended," said Finian. "Naturally, our information was hardly comprehensive. We're technomages, not omniscient. We didn’t know the where of it, for example, or how close to completion it actually was."
-- Armies of Light and Dark, pages 39-43
There is no indication here that this Death Cloud was constructed quickly, since the Shadows apparently did most of the work before they departed. Of course, the technomages had time to learn about the cloud and organize an expedition to Xha'Dam before it launched (despite it being mostly finished by the Shadows before they left the galaxy), so even the completion timeframe is probably more than a matter of hours.
"Care? About things I can't prevent? No, Mr. Cotto, I don't. What I care about are those things I can prevent. Such as the chance that another planet destroyer might be built."
"Another..."
"Yes. Like that one." And she pointed.
Vir felt his gorge rising. For there, still at the far end of Xha'dam, he could see the skeletons being erected already for a second and third Death Cloud. With the finished model as an indelible mental template, he immediately knew the constructs in progress for what they were.
-- Armies of Light and Dark, page 44
These "skeletons" have already been under construction for an unknown period of time. There is no way to tell when construction began; it could as easily be a decade ago as an hour ago.
Even more important, he saw a holographic image floating nearby that he recognized instantly: it was one of the Death Clouds that was still under construction. With horror, Vir noted that the device was already much further along - it actually seemed to be nearing completion.
-- Armies of Light and Dark, pages 50-51
There is no way to tell if the Death Cloud in
this holographic image is one of the two "skeletons" that Vir saw earlier,
since he really has no way of knowing how many are under construction at the
base or of telling one Death Cloud from another. Indeed, he may be
misinterpreting the image entirely; it may be some kind of schematic that
doesn’t reflect the current state of any Death Cloud being constructed at the
base.
To sum up, there is no way to tell how long it takes to construct a Shadow Death Cloud from these passages. Vir saw a complete Death Cloud that hadn’t been activated, two "skeletal" Death Clouds that were apparently in the early stages of construction, and one holographic image that may have depicted a Death Cloud that was further along in construction than the two "skeletons" he had previously seen. It’s entirely possible that three or more Death Clouds are under construction at the same time in this facility in various places and at various stages of completion. There is absolutely no way to tell how long it takes to finish one using Xha’Dam’s facilities.
It’s worth noting, though, that according to the B5Wars game supplement dealing with the First Ones, the most advanced Shadow cruisers take a very, very long time to mature. Following are specifics from the B5Wars supplement Wars of the Ancients.
"Shadow vessels are living creatures bred to serve specific tasks. They normally begin their existence as a small version of whatever type ship they are destined to be, and they grow over the course of centuries. This results in strong ships with extremely capable power generators and truly nasty weaponry. Once the Shadows stopped piloting their own vessels, they embraced the philosophy of quantity over quality, and began to stimulate the ships to grow to maturity over a much shorter of period of time."
-- Wars of the Ancients, page 57
"The Shadow Patrol Cruiser is the first stage of growth of the standard Cruiser and, in Primordial times, the smallest vessel that a Shadow would ever travel in. Respectably agile and armed with a light Molecular Slicer Beam, ships of this class can be raised to maturity in a few short years or even months. In recent times, the newly developed Shadow Destroyer and Scout have replaced the Patrol Cruiser in most surveillance missions, but, due to its short production cycle, it can be seen by the dozen in larger battles, hunting in packs."
"When a Shadow cruiser is allowed to grow over a period of a few thousand years instead of being unnaturally accelerated, the result is a ship with an immensely more powerful propulsion system, weapons with more efficient charge cycles, and vastly improved damage dispersion capability."
-- Wars of the Ancients, page 59
It makes little sense for a civilization that can build a planet-killing super-weapon in hours to spend years building a warship with far more limited capabilities.