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I have always been intrested in Dark Eldar, and now I'm looking to start a army soon. I don't have a codex yet (hoping to have one very soon) I'm wondering what strengths thy have and major weaknesses and also what to start with and any good tactics.
Welcome to the DE forum on LO. DE strengths are speed, iniitative, cheap heavy/special weapons and specialized units. Weaknesses are low T, weak armor saves, outdated Codex (many special rules no longer work as intended since 4th Ed came out), and paradoxically, specialized units. Specialized units are an advantage if you send them against the right units, and a real disadvantage if you use them incorrectly. This is partly why DE are considered a challenging first army.
Read the forum for a while, browse the Army Lists. It might be helpful for you to design a 2000 point list and then break it down into a 1500, 1000 and 500 point list so you can get a shopping list together where you are only buying the models you need for each stage. (unless of course money isn't an issue).
Most people will advise starting with a Lord, 30-40 warriors, a squad of Wytches, 1-2 Raiders and a Ravager. Where you go from there will be based on what type of army you think best suites your playing style:
Kabal - run of the mill balanced list
Kabal - Raider Rush Army
Kabal - WWP
Army of Shadows
Just do forum and google searches on each type, you'll find lots of good articles and threads.
War Record Since Sept 2005
Old Codex 48-20-9 Dark Eldar
New Codex 1-0-0 Dark Eldar