Rider HP: increase
Rider DEF: increase
Rider ATK: increase
Fox is a top-tier hero for a few reasons. She heals all allies for 44% and although with Eve’s other skills she easily outshines Fox, using them together can prove a difficult lineup for an enemy to beat.
Fox can both dispel debuffs and increase defense which means that even though she is a Rider, she acts like a utility type hero in many ways.
Upgrading her to 211 is a must especially if your primary troops are riders, but even if they are not, the fact that she is a five star healer is reason enough to get her evolved.