If your example, why does the reader need to know in advance why everyone is surprised to see a drow? Why do they need to know the entire history of drowdom in order to grasp that it is odd to find one pack in a crate on a ship? Why would it take you an encycopedia worth of words to explain? This is precisely what I object to. It isn't that there is something morally wrong with using someone else's universe, as long as they don't mind you doing so, of course, it's that it leads to never learning how to convey background information. If you continually rely on other people's backgrounds, there's this hole in your writing skills. I'll take your situation and transform it into something roughly equivalent but in my world where the readers don't have any idea of what is going on. When the cruel morning arrived with it's piercing rays, the crew stumbled out of their cabins, and slouched ashore, their eagerness to discover what loot they might have aquired during the night overcoming the drawbacks of minor wounds and sore muscles. The first barrel opened had water, valuable out in the desert, perhaps, but not very interesting here on the banks of the Sanuma. They kept opening them though, hoping that the hob raiders had laid in supplies of something a little more spirited, but when the fourth barrel to be broached let out a wail, they jumped back in startled dismay. My curiosity was keen enough that I actually broke into a trot, ignoring the twinges from my injured knee, and somehow it happened that I was the second one to peer into the dimness, and see some scrawy plucked rabbit of a thingy, maybe three hands long, with pale skin and a face that was twisted up in pain. "What is that thing?" Roaric asked. He'd got to the barrel first and had gotten an eyeful of the creature before comming up for air and commentary. "I think it's a troll," I answered, although it didn't seem possible, and I kept running a mental inventory of what else it might be, because surely it wasn't a troll. Roaric was looking at me like I'd spent too much time star-gazing and was ready for padded restraints and a locked room. "A baby troll," I hastened to add. "I thought sunlight was death on trolls," Roaric responded, still clearly unconvinced. "Ah, yes," that would explain why it was making so much noise. I put the lid back over the barrel and the keening faded away to a pittiful high-pitched wimpering. One of the other men stepped up, and pulled the barrel lid out of my hands, and the keening started up again. He stuck his head in the barrel. "Trollspawn, alright." He anounced, emerging with a stupified expression on his dark face. "Probably best to just leave him. Even at the bottom of a barrel he'll get enough sunlight to be stone dead by noon. But if you can't stand the noise of it..." he reached for his sword, and I grabbed his hand. "Put the lid back on," I told him. "I want him alive." He spat on the ground, and wrestled for control of his sword hand. "They're viscious and sneaky and perishing clever, and nigh impossible to kill. We're lucky to find it so young." "Lucky?" I exclaimed, my voice switching octaves in my anxiousness to get through to the man. "We're in the middle of the desert! That isn't luck, that's slagging impossible!" He stepped back and I let go of his hand so that I could grab the lid back, and place it back on the barrel. He looked at me in astonishment, and I could see the gears turning behind his dark face. "So how did a troll spawn make his way out here?" "Naw that's clear enough," Roaric responded. "He came packed in a barrel, and the hobs was carrying him. What I want to know, is why?" Okay, so what do you need to know in that passage that you didn't get?