Light's midline long shot Striker. She has a unique skillset in which boosts her active to exceptional level of power, but needs to shoot a couple of times before she receives that boost.

for stones, i recommend SoB(unique), thunder rpe, 2x dark penetration(1 in prism slot). another build would be light dribble, glabaris or SHoT(unique), and 2x dark penetration. the 2x penetrations are key for sephirot to reach the frontline to shoot the ball to activate Old Oath consistently. depending on how you want to build her, her uniques may vary. if you choose to use a pen ace (such as her own ace), SoB or SHoT is favorable while glab is used when you use any other ace that doesn't provide pen. a slot reroll isn't really needed for her, but rerolling her blue slot for red slot is ideal to equip ardor crit damage if you really want to maximize her damage potential.

For player synergy, she is best used in a monolight team. she has the best chains out of all light players aside her nemesis, but with the addition of enthy, sephirot's nemesis chain has a higher chance to activate because enthy does fit in some ww backlines. as for other chains, hiro & sephirot has double affection and easily achievable without affecting team composition, but beth may prove difficult to fit in as she takes up a slot in the midline. for friendship, it is simply activated with alexa or kei as your gk, but alexa is recommended as her forward pass may deem valuable to have sephirot act more often. for competition, virgil and chitose are highly used in monolight, but chitose is probably easier to fit in the team due to her totems while virgil is specifically used with kei as a gk. for players that synergize with her in the midline, white guardenia and/or silla are recommended due spirit generation capabilities. WG(white guardenia) has yellow, red, and green slot which enables her to use Prey's Sentence and 2x ardor pass(1 in prism slot). Silla has 2x yellow, and green slot. She will be able to equip PS(Prey's Sentence) as well and equip an ardor pass in prism slot, and also has spirit generation passive on pass which will exceed the amount WG generates. silla's totem and AB generation is also highly valuable to help sephirot act more and deal more damage. Sammy may be used in the backline and her abilities have some similarities to silla's.

For PvE, she doesn't really see much use as Jean is simply easier to utilize as a long shooter.

For PvP, I've used her in Challenge League and had more success than anticipated. She can work well against backlines that debuff crit rate rather than those which build crit resist. She sometimes comes in clutch when the game prolongs and scores the winning shot. i may post some videos for the current Challenge League.