|A build that those with the fodder (and feathers) to spare can run with on their Armor Emblem teams. Hone Armor support at the very least is suggested, especially if you're like me and find yourself a F2P with a -Atk IV Lyn.
Weapon: It can seem like a waste to cast Lyn's Blue Gift+ aside, but if you don't find yourself in need of a neutralizing tome (for example, you might have a Henry: Happy Vampire with a Spectral Tome+ on your team to do more than neutralize buffs), Blárblade+ comes in to give Lyn's Atk stat a potential boost. Ignoring the fact that her default A slot gives her a sizeable combat bonus already, Blárblade+ paired with Armor Emblem buffs is just what the summoner ordered this Valentine's Day. With an already respectable Spd stat of 36, a single Hone Armor support shoots Lyn up to 42 Spd. Now, let's stop ignoring her A skill and add 5 more Spd from whomever's got Lyn's back - She's now ascended to 47 Spd. Not bad, when you also remember that she's just gained at least 6 Atk as well (with 6 from Hone Armor and 5 from Atk/Spd Bond 3).
Assist: You really can't go wrong here with any of the movement-based assist skills we have; some people rock Reposition, others like to mix it up with Draw Back, and plenty of other people can feel comfortable with Swap or Pivot. You know your own play-style better than anyone, you do you. However, for those looking to conserve resources, Lyn's default Ardent Sacrifice works perfectly with a Desperation 3 build (provided she's not +HP IV).
Special: Glimmer is the first special that comes to mind for some people when eyeballing a build like this, and considering the synergy with the way blade tomes work, it's a solid choice for any player-phase unit. However, specials like Draconic Aura and Iceberg are well within the realm of possibility should you want to opt for those instead, especially in combination with a certain Sacred Seal.
A Passive: Atk/Spd Bond 3 is just fantastic. +5 Atk and Spd during combat just for having Lyn stand next to her Hone Armor partner like usual, or another ally? Love is in the air indeed. However, should you find it difficult to always have someone next to Lyn when she initiates combat, there are of course other options. Should you find yourself desiring some synergy with a B slot skill, Fury 3 might work well paired with Desperation 3.
B Passive: Speaking of B slots, if you didn't get a -Spd IV Lyn, this is yet another slot open to your own play-style! Those looking to save some resources can feel fine staying with her default Guard 3. But for those interested in other ventures, Desperation 3 plays well with Fury 3, as well as without it (provided Lyn has taken a counterattack or two). At a base 37 HP, Lyn need only take 10 points of damage to activate the effect, and with proper support, she's likely doubling the opposition.
C Passive: Armor March 3 is Lyn's default C slot, and it's welcome news to those who've managed to miss all other sources of it. A staple of Armor Emblem teams, it's perfect for those looking to conserve resources as well. If you already have multiple sources of it in place on your Armor team however, this slot opens up to suit, you guessed it, your play-style and/or the needs of your team/Lyn.
Sacred Seal: This is yet another "free" slot, open to be occupied by whatever Seal your Lyn needs at the time. Distant Def 3 probably wouldn't hurt in case of enemy phase combat (pending a Desperation 3 build), but for those looking to mitigate the cooldown-downside of Blárblade+, Quickened Pulse can give Lyn a jump-start at the start of every map. Did someone say Tempest Trial? Furthermore, if for whatever reason that isn't in the cards, due to the way Blárblade+ functions you may also opt for Heavy Blade 3 in combination with Glimmer, although some would consider this overkill in many situations, and it is not efficient when using Desperation 3 and in the effective range.
Author's Notes: This build has weaknesses, just like any other build. Aside from the usual tactics involved in playing your units, this Lyn needs to watch out for any enemies running Panic effects. At 37 base HP, this Lyn is a prime target for Panic Ploy 3, and it can be devastating. Oddly enough, one source of Panic is her fellow Armor Mage Henry: Happy Vampire, whose tome effect can often (but not always) overshadow Lyn's default tome, as mentioned beforehand. A properly built one makes a decent teammate, but is by no means necessary of course. On the other hand, a Tharja: "Normal Girl" with Hone Armor and perhaps Swap makes an excellent teammate, as keeping her by Lyn's side would not only keep Lyn buffed, but also provide a bulky shield against any green units that might be lurking behind Lyn's targets. I realize of course these are both seasonal units that not everyone has, but again, they are just examples. Any teammate running Hone Armor is sure to be appreciated by this Lyn.