Legendary Lyn

Preferred IV: +SPD or +ATK / -HP or -DEF

Making use of the upgraded Laws of Sacae II L!Lyn can operate as a dual phase hero targeting melee on player phase and tanking ranged on enemy phase.

Weapon: Swift Mulagir

Swift Mulagir is the ideal weapon of choice, being able to grant Legendary Lyn with 5 Attack/Speed if she is able to meet the activation condition. This offensive boost can help to provide her the means necessary to activate both Laws of Sacae II and Flashing Blade 3's Spd requirements.

Assist: Reposition / Rally Def/Res / Player Preference

Reposition is generally a useful movement Assist for many units, allowing for a swift retreat or the ability to help an ally advance.

Rally Def/Res is the skill included in Legendary Lyn’s base kit, and can function just fine if one is not willing to change the Assist skill.

Special: Moonbow / Luna / Iceberg

Moonbow is able to be activated every round of combat provided Legendary Lyn can meet Flashing Blade requirements and is not hampered by Guard related skills.

Luna and Iceberg provide a larger source of burst damage than Moonbow. They are excellent choices to run if Legendary Lyn is not running Flashing Blade as the Special should activate roughly every other round of combat.

Passive A: Laws of Sacae II

The upgraded Laws of Sacae II gives Lyn a needed boost to her stats for offensive and defensive situations and additionally offers a solution to distant counter wielders so long as her Spd can sufficiently outclass her target.

Passive B: Lull Spd/Def / Chill Spd / Chill Def

Lull Spd/Def not only inflicts -3 Speed/Defense on her opponent, but it also helps Legendary Lyn to ignore Speed and Defense displayed buffs that the opponent may have. Thus making it far more likely she meets Flashing blade and Laws of Sacae for faster specials and denied counter. Chills are less immediately useful by comparison, but they are both accessible through the usage of Grails via Panne and Walhart respectively.

Passive C: Joint Hone Spd / Spd Tactic / Def Ploy / Spd Ploy / Player Preference

Joint Hone Spd is an excellent skill that rewards Legendary Lyn and her partners for playing off her playstyle of keeping close to one another. Giving a 5 Speed buff to Legendary Lyn and her allies next to her at the start of combat ensures more reliable follow-up attacks for both Lyn and her friends.

Spd Tactic is the skill that Legendary Lyn comes with on her base kit, and due to the relatively rare nature of Spd Tactic, it can be a solid option if Legendary Lyn is on a mixed team. However, Spd Tactic does not benefit Lyn herself compared to Joint Hone Spd.

Def Ploy and Spd Ploy can be fairly reliable with Legendary Lyn’s naturally usable Resistance.

Sacred Seal: Flashing Blade

Flashing Blade Seal is here for handling repeated Moonbow activation duty.

This build is to maximize the offensive potential of legendary lyn, the combo of candlewax and life and death gives an fabulous +8 atk/spd while only reducing her defense and resistance in 2, she will hit hard and get into the range of desperation quickly and assure kills, def smoke is for either a dancer refreshes lyn and attacks again or for team mates to take advantage of that debuff. Sturdy blow is there mostly for more attack in player phase that's all and rally atk+ for a bit of support.
The special is glimmer because she will constantly deal high damage and with this special that damage is intensified even more

Seal: Distant Def or HP/Res2
B alt: Vantage
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Lyn's kit emphasises ally proximity--and Blue Flame is a shiny new toy that would benefit her greatly due to sheer likelihood that she will be adjacent. While gaining around +7 res from allies is perfectly doable on enemy phase for Iceberg, Blue Flame can allow for player phase procs as well. Her B, C, and Assist are all rather flexible. She shines as a supporter and mage baiter, and can probably take bows and knives on occasion. Ploys, rallies, Spurs, drives, Infantry Rush/Flash, etc... can all work well and she will not have to worry about leaving herself vulnerable after assisting her allies.
Preferred nature would +HP -def as the superboon would allow for her def to be effectively a net gain of 1 if she avoids multiple physical engagements as her spd is high enough that she will not have to worry too much about getting doubled. However, this would interfere with any potential to ploy as 30 is rather low for my liking and 32 with the HP/res seal is at an uncomfortable bare minimum of the threshold.

While at first it may seem as if Lyn has poor defenses, when invested enough in they become pretty good. This set aims to make use of her unique skills in order to turn her into a capable ranged tank. By stacking Swift Mulagir, Laws of Sacae and Distant Defense Lyn is granted +9/9/10/10 to her stats; with a boon in speed and a bane in hp this rounds up to 54/48/31/40, which are good enough to avoid and sometimes procure doubles, while taling little to no damage from blue and green ranged units. If you want her to perform as less of an all rounder and more of a res tank she can take a bane to her defense instead of hp to keep her magical bulk intact.
The rest of her kit can vary without having much influence on her playstyle. For her b slot, Dull Ranged further cements her as a ranged tank, while quick riposte can be taken if her speed doesn’t seem enough to double enemies or if a speed boon wasn’t avaiable. As for her special, moonbow and glimmer work perfectly if she’s not expected to enter combat more than once per battle, bit she can also charge iceberg for use in the player phase or glacies to proc in her next bait.

Boon/Bane: RES+ / DEF- best, anything but Atk- or Spd-
Weapon: Swift Mulagir
Special: Glimmer / Luna / Moonbow

Basically turning L!Lyn with a potential unfavorable boon into something usable. With Swift Mulagir and a RES boon, she hits 33 RES without merges, enough to Ploy a fair number of non-mage enemies. Ploy choices can vary based on her role and team comp, but the selfish choices for Lyn are definately Spd and Def Ploys. If managing to land the ploys and proc Swift Mulagir effect, Lyn can likely forgo needing Swift Sparrow and opt in for the slightly more accessible Death Blow 3. Glimmer is the preferred Special since Luna/Moonbow will be less effective against a DEF Ployed enemy, though Luna/Moonbow fit one of her attack lines much better (“One arrow, one kill!”). All in all, a serviceable debuffer archer and a standing buffer during Wind seasons.