I was under the assumption that maxing out the stats helped your characters. For example, my Jade Oni had the "Myth-Shot" ability which added 2% of accuracy as an adult. It went up as my Jade Oni's stats went up, so it's at 5% now. I'm still confused though. For example, under the strength category it reads, "Strength affects damage, pip chance and resistances". My Jade Oni is maxed out on strength, yet his spell still does the same amount of damage. Shouldn't his spell be stronger since "strength affects damage"?
No, because the strength skill only effects any traits that your pet gets that are for damage, pip chance, or resistances. For example my Stormzilla pet has a trait that gives me Storm resist while in battle. When my Stormzilla was still younger it only gave me 3% resist, but now it gives 8% resist as I have maxed it's stats. The spell card that your pet gives you will not change because of your pets stats. It is not a representation of your pet, simply a spell card that happens to look like your pet.
I was under the assumption that maxing out the stats helped your characters. For example, my Jade Oni had the "Myth-Shot" ability which added 2% of accuracy as an adult. It went up as my Jade Oni's stats went up, so it's at 5% now. I'm still confused though. For example, under the strength category it reads, "Strength affects damage, pip chance and resistances". My Jade Oni is maxed out on strength, yet his spell still does the same amount of damage. Shouldn't his spell be stronger since "strength affects damage"?
Increased damage means if the pet gives you a school or general damage boost, it relies on that stat. The spell always uses your stats, which may or may not be affected by your pet.
