Information - Battle

Simply put, in battle, Emeralda is frikkin' awesome. She is fast, she hits hard without any weapons that have to be bought (one of the main reasons I love Fei and Citan), and her ethers are useful in those rare situations when enemies need an elemental beating.

... yeah, there isn't much else to say. Just that Emeralda in your party is super-awesome. Why anyone wouldn't want to use her is beyond me.

Just for the sake of completeness, here are a list of her deathblows.

Leg Cutter: T, X
Wave Cutter: T, T, X
Leg Spin: S, X
Hammerhead: T, T, T, X
Grand Arm: T, S, X
Divider: S, T, X
Flying Arm: X, X
Tornado Arm: T, T, T, T, X
Reycount: T, T, S, X
Dark Beast: T, S, T, X

Watching Emeralda's battle animations isn't anything short of amazing. In case you've been living under a rock, the reason Emeralda as a little girl is such an amazing melee fighter is because she is able to change the shape and properties of the nanocolonies residing in a limb or even her hair to become hammers, morning stars, and blades.