Have you read Poems of Heaven and Hell from Ancient Mesopotamia ? It's a good source for myths about ancient Mesopotamia. I haven't looked up info on Erishkigal on the internet before. If you look at the thread stuck at the top of this forum, there might be a website where you can find Erishkigal info. Also, you can try www.pantheon.org
I think that we are drawn to deities who have a darker side because of our need for balance. Everything in life is not always peachy. We have dark/light; love/hate; happiness/sadness...etc. These deities might give us the justification for this balance. Some deities who are darker teach us to be strong. I think that we can find inner strength when turning to them for guidance.