I did a lot of character artwork in preparation for Invasion, starting with model sheets that other artists taking part in the crossover could use. These weren't professional-level model sheets — I don't think I've ever done any of those, and in this particular case, the artists would be free to reinterpret the characters in their own styles. I just wanted to lay down the important characteristics of each character.
Model sheet for Atra, including her colour scheme. This one only showed the older Atra - I didn't know until much later that her rejuvenated form would make an appearance.