The EldarThe Eldar are an ancient race that was once extremely powerful and even dominant, but has kinda been reduced to terrrible terribleness.
A little bit of history...The Eldar were a pretty freakin' baller race. Unfortunately for them, the keyword of the last sentence was WERE. They have had a long fall, from a pretty great pinnacle of awesomeness. But we're not here to discuss their current situation, no, we're discussing history! So anyway, back to the beginning.
The Eldar are ancient. I mean, old. They've been around the block a couple million times. Anyways, because of this, they've had a while to make themselves the best around. To start, all Eldar are all psychic. That's pretty cool right there. Second, they can make entire worlds. Kinda overshadows the first thing, maybe should have been first, but their world-making really depended on the first part. So anyway, they were the stereotypical super-advanced alien race that was better in every concievable way than humans on our best super-sunny day. Because of this, as you might have imagined, they had a lot of free time, considering they didn't really have to waste their (oh by the way) next to immortal lives doing menial tasks to improve society seeing as their technology did it for them. The society was fine, so they realized they needed to start doing things to pass the time. This is where things started going awry.
Thinking about writing this paragraph, and realizing that I've already written it...so why don't you go pop on over to the Dark Eldar
page? Yeah, you read that right, the Dark Eldar DID have something to do the Eldar! Betcha didn't see that one coming...
So anyway, that whole 'creating a chaos god with our excess and through that annihilating most of our race and turning the space where our homeworlds was into the largest Warp incursion we've seen so far' happened...not really a high point for the Eldar. At this point, the rest of the Eldar (those that were left) got the hell out of there. This is pretty much where they're at right now (in lore), which is basically an ocean of suck. They are still pretty awesome, but they aren't increasing in number, in fact, their numbers are decreasing steadily. They really need to get their shit back together and...repopulating their race. Bow chicka bow wow.
In reality...If you're thinking about playing the Eldar, look no further. Simply visit this page: Eldar Success!
Seriously though, for the most part, the problem with the Eldar is the same as the Dark Eldar...that damn Toughness Value of 3. Equals boltered to death.
Fortunately though, since this is the way the Eldar have been for quite some time (walked all over), their new book may have them come with actual BALLS, which would be nice.