Slaanesh seems forgotten in this game, why? And no mention of one of the dual supplements containing slaaneshy content. Any ideas?

Also normal "dark magic" not including it's many variants (chaos, necromancy, etc.. ) doesn't contain that many spells, and with the PC's ability to lean it, many of the action cards don't make sense with the NPC's converting fatigue into wounds. Any one have ideas for more of those? like Chill wind, word of pain, and blade wind?

I'd make suggestions myself, but I don't know enough about the game I just have nearly all of the suppliments (minus the Adventurers vault).

Slaanesh is most likely going to be the next bigger supplement after Black Fire Pass. No official word on this yet though.

As Doc mentioned Slaanesh is in the offing and will hopefully be on the calendar for Q4 2011 or early 2012. In terms of Dark Magic, FFG hasn't put out a lot of player character inspired spells yet. I would imagine we'll see a "playing a bad guy" supplement at some future point, but that could be a ways off seeing as they have some more common ground to cover. Until then, download Strange Eons and start making up your own vile darkness for use with PC's. It's fast and easy and if you are worried about game and setting balance with house-rules you probably wouldn't be playing a Dark Elf sorceress in the first place

Oh I use Strange Eons, it's awesome. I was just asking for advice on creating new spells, I'm new to the game so I am scared of imbalance.

You could go the witch route (which would fit Dark Elves pretty well) and pick up spells from multiple orders as mentioned above. Since you are comfortable with using s.e you could just nab some order-specific spells that you like and come up with a dark magic flavoured versions. The effects will essentially come from the cards you are emulating, but your custom names & description of the spell effects will be adequately Gwar.

If i was going to just nab spells I'd probably not make new cards for them =P but I'll take a look at the witch while i'm at work today.