@ dystopic, you are 90% right and I am not saying you are wrong so never think that! The Drakh retained the advanced technology and aggressive Philosophy of the Shadows. With the destruction of Z'ha'dum, those beings (Drakh) that had faithfully served the Shadows down through the centuries found themselves homeless. Now these thralls (Drakh) sought to become masters of Chaos themselves. Thus, the legacy of the Shadows lived on.
Unlike the Vorlon Planet Killer, which used a massive energy bolt to obliterate a planet, the Shadows took a much more conservative approach to destroying a planet. The rationale behind this was not one of efficiency, but rather the promotion of Chaos and strife — while the Vorlon method is swift and deadly, thus exhibiting their "punishment" of races who have become "disobedient" to them, the Shadows preferred to prolong the fear and panic brought on by their rather imposing weapon, sowing more and more Chaos with each passing minute. Also, by leaving the targeted world intact but defiled, the Shadows left testaments to their work for their enemies to see.
So that makes me 10% right, I just conected legacy with the two, Philosophy and Chaos.
Philosophy of the Shadows is survival of the fittest and the Masters of Chaos so you are right and me too.
Kzinti Empire is good example of that Philosophy, they are on top and they are Masters.