[BWStripes]

You can either "count" the mobs that die if you are sure they will not die simultaneously, or if you have a lot of mobs that might die at the same time, this method works better:

sub EVENT_SIGNAL {
    if ($signal == "blargdeath") { # Signalled when something dies. Diediediedie. Die.

        $mobcheck = $entity_list->GetMobByNpcTypeID(xxxxxx); # Mob id xxxxxx that must 'not' be up

        if(!defined($mobcheck)){ # You sank my battleship.
            quest::spawn2(xxxxxx,0,0,$x,$y,$z-10,69); # Spawn something else
        }
}

And in each of your mobs that is meant to die, the trigger code:

sub EVENT_DEATH {
	quest::signalwith(xxxxxx,"blargdeath",0); #Signal mob id xxxxxx that we died
}