: When all the Fallen Lords are killed, the magic which
: animates the armies of the dark fails, and all of the
: walking dead fall in their tracks -- That's correct,
: right?
Depends on the circumstances. Balor bound most/many of his undead soldiers to him in such a fashion that they were either weakened or destroyed when he died. Many other Fallen Lords, however, do not necessarily do this. Soulblighter's army had to be finished off by hand, regardless of whether or not he was destroyed.
GURPS says that in some places where travel is difficult--swamps and such--you'll find a few undead who got stuck and left behind in the march of a Dark army. Watch your step!
--SiliconDream