Stats Guide - Soul Energy

The Soul Energy (or "SG"; it is sometimes still called "SoulForce" or "SF" by older players) is like your mana in other MMORPG games.

The SG is partially consumed each time you use a skill and can be recovered by several ways depending on the character you play.

Basic attacks are generally used to recover your SG (the only exception being Stella who can't restore her SG through basic attacks). Some skills on some classes can apply a buff on SG restoring or recover SG through hits landed. There are also some A.R cards that can restore a part of your SG by meeting special conditions. Finally, some set/upgrade effects on gears/jewelry can restore a part of your SG as well or reducing its consumption.

Lily has a damage and crit rate passive buff which is triggered by her SG bar's state, so it is important to keep an eye on it while playing with her.

The Soul Energy is a core mechanic of this game and badly managing it results in a performance loss in general.
There are, of course, several way to restore your SG and managing it easier. One of them is to use the Reduced SG Consumption stats, which can be acquired through endgame gears' set effects.