IMC, Humans have become the dominant sentient species, largely because they have almost continually waged war against the monsters and other demi-humans throughout history. Some sages ascribe this to a sense of "manifest destiny" on the part of the humans and other believe it is simply because humans have a higher degree of adaptability (extra feats and skills) than most other sentients.
In actuality, the massive historical expansionism by the humans is the direct result of machinations by the so-called "Trilateral Commission", the three principal entities of which are The Torchmakers Guild, The Lamplighters Union, and the Lamp Oil Producing Entities Collective (LOPEC). The Trilateral Commission has poured literally millions of gold pieces into mercenary armies, bribes, undermining foreign economies, etc. to see to it that Humans conquer and displace their enemies, thereby establishing themselves as the dominant race on the planet. One that needs to see in the dark.
Of course these other races fight back and, since they all have low-light or darkvision, they often attack at night. Since their human foes need illumination to counteract this threat, they use even more torches and lanterns, resulting in what the Trilateral Commission furtively refers to as Step 3 (profit).
What the TC doesn't realize is that there is a growing threat to their stranglehold over the course of human events: DPI (Deity Powered Illumination). Underground races, primarily the Dwarves, have been selling finely cut rubies to the humans for years. In the process they have accumulated enormous piles of seemingly useless ruby dust. But they now realize that for the cost of this otherwise useless dust and a few 2nd level spell slots, they can start creating Continual Flame torches by the cartload.
Once this cheap and endless source of light hits human lands in great quantity, the results for the TC will be disatrous. LOPEC will fold almost overnight as their richest customers flock to the use of Continual Flame torches. The Lamplighters Union will soon folow. The Torchmakers Guild may limp along for a bit longer, counting on the fact that their product costs a commoner only fraction of his day's wages. But The Torchmakers Guild was always the "red-headed flumph" of the TC anyway and they will never be able to get by as a "Unilateral Commission" by themselves.
Without the massive monies of the TC funding the various mercenary armies and bribes, human expansion will grind to a halt. The various other races of the world, so long put upon by the human scourge, will rise up together and strike back, erasing decades of gains by the humans. It will be a bleak time for the once mighty Men of the world.
But just when things look their worst, LOPEC will come to the aid of the humans once again. Reminding the generals of the human armies that oil isn't just for light anymore, they will show up with catapults and barrel upon barrel of the flamable substance in tow. The humans will be able to employ these infernal devices against the masses of orcs, dwarves, goblins and elves who array themselves against their empire (in tightly packed formations). Best of all, not only will they be able to use the oil to set their enemies on fire, but they can also SEE them burning at night! From a distance of greater than their enemies 120' darkvision even!
Thus will the humans enter a new golden age of lighting things on fire...
Well, not really. But maybe next campaign.
