system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40k] Has the imperium cured cancer?
gpt
The mechanicus discovered an STC capabele of curing all disease, in preparation for it's transport to Mars they deployed a titan legion, several companies of Astartes and more Imperial guardsmen than you can count to protect it.

Of course, since this is 40k, something was bound to go wrong. So the Dark Eldar invaded in force. 

Why?

Litteraly to prove that of all the Dark Eldar, that particular leader was able to pull the biggest dick move in recent history.