Welcome. I've found that after starting Dark Eldar, I have difficulties playing other armies. They are so slow! What do you mean I can only move the vehicle six inches and shoot a single gun? Wha? I wasn't able to assault after running?
Browse around, look up some tactics and check out some galleries for inspiration, and most of all, practice, and you'll be slaughtering and enslaving the lesser races with no problems!
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Siticus Empyrean Vision - my Facebook page with various painting projects
Siticus' Empyrean Visions log - the project log for my Aeldari works and beyond