it's in the head
Alien is not whether you know what goes on in their society or not - alien is what goes on inside their heads. In order to make Drow more alien, you need a good rationale for them to not think (and thus not act) the same way we do. Think about it: what makes being in the same room as a sociopath unnerving? It's not that you don't know anything about sociopaths, nor really the whole violence thing; it's that the internals of their mental structure are very different. You can't model it well.
To see a very extended example of (very) alien built on a good backdrop, have a look at this:
http://www.nada.kth.se/~asa/Game/Countdown/index.html
For a less alien example, but one that should still make most people pause here and there, there are my Datarii or Ennierd from Principia Infecta - both races that do a fair job of interacting with people in a normal way, but have societies that just couldn't exist for humans. This is due to fundamental, but subtle, differences in the way in which their minds work.
Anyway, my point here is you need to explore the mind and the precepts - and then extrapolate to the society that would result in. That is what builds alien. There are a great many good works of science fiction out there to help you with this sort of thing - it's a rich vein for some writers - such as the Left Hand of Darkness.
Reason
Principia Infecta
Alien is not whether you know what goes on in their society or not - alien is what goes on inside their heads. In order to make Drow more alien, you need a good rationale for them to not think (and thus not act) the same way we do. Think about it: what makes being in the same room as a sociopath unnerving? It's not that you don't know anything about sociopaths, nor really the whole violence thing; it's that the internals of their mental structure are very different. You can't model it well.
To see a very extended example of (very) alien built on a good backdrop, have a look at this:
http://www.nada.kth.se/~asa/Game/Countdown/index.html
For a less alien example, but one that should still make most people pause here and there, there are my Datarii or Ennierd from Principia Infecta - both races that do a fair job of interacting with people in a normal way, but have societies that just couldn't exist for humans. This is due to fundamental, but subtle, differences in the way in which their minds work.
Anyway, my point here is you need to explore the mind and the precepts - and then extrapolate to the society that would result in. That is what builds alien. There are a great many good works of science fiction out there to help you with this sort of thing - it's a rich vein for some writers - such as the Left Hand of Darkness.
Reason
Principia Infecta