User blog comment:ChishioKunrin/Let's Talk - Beginning of the End/@comment-5414218-20160103174245

It's left very clear that Mercury was the one that killed his dad. We don't know why but it's obvious considering the scene and the fact that Cinder mentioned they saw the fight between the two.

Maiden's powers not restricted by one element was a surprise but I wonder now if all the maidens have the exact same powers or if there are some key differences between each other's.

I doubt there's anything important about Cinder's tattoo, probably just to represent the her "half-maiden" status.