“As time went on, Fox grew to be an integral part of the Fantasy Force, even to the point where even Shieldrush trusted her with his life.”
As time went on, Fox grew to be an integral part of the Fantasy Force, even to the point where (TAKE OUT EVEN) Shieldrush, one of the most cynical/skeptical/xenophobic members trusted her with his life.
Better to avoid repeating the same word by being more descriptive. You seem complete enough. I would have to know more specifics about your goals (intended audience, intended tone/style etc.) before I could do much more–your grammar and spelling are obviously okay. 
