Norne

"Your defeat is Norne of my business" general build
(i have never use her in AR specifically but for general use this is worth the try for me)

another one from me, a Plegian Bow+ equipped Norne that obliterates anyone (exception for units with Unity skills, Fallen Ike's Chaos Ragnell, other units with effects that neutralizes penalties on them in combat, and heavy-booted armored unit, they should move fast istg). i can say i'm happy with this investment after foddering 1 Plegian Raphael that i supposed to keep because i insisted in trying this build and i'm on my way to +10 him so wish me luck in getting 3 more of him from the Plegian banner before it leaves.

Weapon: Plegian Bow+ (Spd) / (Def) / (Res)
She'll maximize the Atk/Def penalties she'll inflict to foes with the Def Smoke on C slot and Atk Smoke on Seal, so this is a nice option for her to use as long as you can keep her alone with no allies adjacent to her (this is due to the weapon itself). Spd refine can get her a follow-up attack to that foe and would keep her safe from getting doubled.

Assist: Reposition / (Your Preference)
Any assist skill is fine for her to look out for Marth but her default assist skill Reposition is nice too.

Special: Deadeye / (Other quick specials)
You're gonna have to fodder Shinon that you pulled somehow for this special skill, but other options are fine too! (such as Moonbow or Luna to drop foe's defense, Noontime or Sol to keep your Norne healthy to survive in this crazy world, Bonfire to use her defense stat against an even unit with the same amount of defense so she can flex to them and Marth, and Draconic Aura or Ruptured Sky to use your or their attack stat for her advantage in defeating them (Ruptured Sky will take her beast and dragon foes she faces to not exist, so this is another best option i could think of considering she'll use this A skill to counter all range). i'm not gonna lie, i think any quick specials are fine for her because her weapon helps her defeat the foes (with that exception up there in mind) regardless.

A slot: Close Counter / Close Foil / Close Ward
I use Close Counter to beat all types of unit even dragons! Close Foil is another nice option to beat all physical units. Close Ward is okay too! another option that you need to fodder NY!Plumeria first to get the skill to defeat all dragon foes.

B slot: Lull Spd/Def / Atk/Spd / Atk/Def / Null C-Disrupt / Vantage
Her best yet skill on this slot for this build is Lull skills, she'll respectively add more stat reduction to foes with this, so i personally go with Lull Spd/Def to add her attack and get her even faster. Atk/Spd: to get her faster and bulkier, Atk/Def: to get her even more beefier. Null C-Disrupt will help her stop the effects of preventing her from counterattacking so this is an option too. Vantage! like my previous entry of Norne, is okay too if you don't have any fodders to get those skills i've mentioned for this slot.

C slot and Sacred Seal: Def and Atk Smoke 3 (respectively)
Here it is, these slots are the deal breaker for this build, so obviously you'll need these two to maximize her use of the weapon even further. Def Smoke 3 to get the foes' (within 2 spaces of target that you defeat first) Def lower than her so they beg you to not beat them up after you inflict them with it, and Atk Smoke 3 to get the foes' (within 2 spaces of target that you defeat first) Atk lower so she can survive more longer while they still beg you to not beat them up after you inflict them with it. (in combat debuff total on foe = -12) + (visible debuff total = -7) = -19 to both Atk and Def of that foes' each stat.

Weaknesses of this build (or the weapon in general):
-Unity skills
-Fallen Ike's Chaos Ragnell
-Skills with effects that neutralises penalties on them during combat
-Slow-moving armored units (they cannot hit you if you don't get close to them, could be bypassed if you hit the unit that's adjacent to them first)

Boon: Atk
This build takes advantage of the Helm Bow+'s ability to nullify the opponents buffs. By giving her Lull Atk/??? 3, she can effectively nullify every one of the opponents' buffs that matter to her. Take Lull Atk/Spd 3 over Lull Atk/Def 3 just in case there is ever a situation where she cannot activate the Helm Bow+'s ability, she has the best survival chance by nullifying these buffs and lowering these stats.

For the Assist, you can just leave her Reposition alone, unless you want to use her for Arena. However, there is a special case where you can give her shove or smite to potentially avoid ending her turn standing next to an ally on enemy phase.

For the Special, Noontime can help her sustainability. If you want to do some extra damage, Moonbow or Glimmer will work perfectly. In order to maximize her Helm Bow+ use, avoid Blue Flame.

A and B Skills have no major alternatives.

C skill is best to increase her killing power or sustain, so any Joint Drive skill will work. Alternatively, use Pulse Smoke 3 or Def Smoke 3.

For the Seal, Quick Riposte 3 can't go wrong. Alternatively, use a seal that can increase Def/Res or sustain like Close Defense 3, depending on the situation.

My Unit's Stats (ATK Boon): Merge +10 | Summoner Support | 4 Dragon Flowers
Rating (Per Arena): 224
Base Stats: HP 54 | ATK 54 | SPD 45 | DEF 38 | RES 33
Effective Stats (In-Combat in Enemy Phase) : HP 52 | ATK 71 | SPD 48 | DEF 53 | RES 43
Effective Stats (In-Combat in Player Phase) : HP 52 | ATK 66 | SPD 48 | DEF 48 | RES 43
HINT: Pair her with L!Eliwood using Smite and allow her to receive his Bonus Doubler Buff and she will kill almost anything that tries to kill her. Also, maybe bring a Dragon with Eff against Dragons weapon. Another cool combo I tried: Partner her with Lilith and have Eliwood Smite Norne into attack and Lilith follows-up after (I bet there are other great partner combos for her that I just haven't tried...)

Weapon: Spendthrift+ (+SPD)
Special: Noontime or Moonbow -In my experience, she doesn't need extra damage to kill because she has incredible staying power, and Noontime usually results in her getting a few HP per engage, but if you need the damage Moonbow is best.

A: Close Foil, unless you want her to counter dragons as well then go for full Close Counter.
B: Lull Atk/Spd 3 (Spd/Def is also nice, but something with Spd is ideal for best doubling chance) or even Mythic Boost for better ranged tanking.
C: Joint Drive Atk (Natural choice to improve her low base attack)
Seal: Close Defense is my go-to default, but lately I been trying our Sorcery Blade (which cannot be selected from this sites' dropdown menu but can be selected in game) as it can help her to shred more easily through even the most stubbornly tough tanks. Ultimately, her seal is highly versatile.

This chic has recently been my Queen of Aether Raids & Rokkr (especially against flying units, easy 200k scores with her on your team), and I'm even using her in Arena a LOT now that I have her fully merged and she has a really decent rating of 224. I am already concerned about how she has taken the dominant spot in all my new theory-crafting teams. She is amazing & this build rocks.

Double Phase Norne (for general use)

i personally love this build i've invested myself, Norne with speed asset guarantees her to make follow-up attacks or keep herself away from getting follow-up attacks against her opponents on both phases. plus Louise's inheritable bow with Spd refine can make her even faster and able to trigger Flashing Blade 3 Seal on player phase so her special can reduce it's cooldown immediately to be activated for the target she's facing or other targets she'll encounter. While on enemy phase, she's capable on defending herself against melee and physical opponents thanks to Close Foil for the additional Atk/Def to strike back and survive (you can use Close Counter right away if you want to counter dragon foes as well).

Aether for the HP recovery so she can survive a bit longer while dealing damage to the enemy, but you can use other special skills with less cooldown for faster approach. Vantage 3 is pretty self-explanatory. Def Smoke 3 for more offensive pressure against the opponents.

Alternatives:
Special Skill: Moonbow or Luna
A Skill: Close Counter
B Skill: Lull Skills (Atk/Spd or Atk/Def or Spd/Def)
C Skill: Atk or Spd or Pulse Smoke 3

Rather expensive, but extremely effective. This is a high octane investing build; only do this if you are completely serious about using Norne.

Weapon (Fishie Bow+ {+Spd}): Fishie Bow is an amazing weapon, granting bow units the Desperation effect while leaving the B-Skill open for other infantry skills that could suit her better than desperation.

Support skill (Reposition): This one is up to you. I'm using Reposition because it's my favourite support skill, great movement capabilities and very cheap. However, I'm aware that some people like to use Draw Back instead, or the Rally+ skills for arena purposes.

Special (Luna): While her speed is fantastic at a 36, her mediocore attack stat of 32 leaves room for improvement. Luna is great for units with lower attack halving the enemy's defences. Not only that, but the 3 charges of Luna synergize perfectly with her B Skill Special Spiral. However, if you choose not to run Special Spiral and choose something like, let's say, Lull Spd/Def or Null Follow-Up, Dragon Fang or Astra can prove to be excellent choices as well.

A Skill (Fury 4): Fury is a great skill for Norne. It gives her buffs to all of her stats, while also helping decrease her Hp into the "under 75%" zone for Desperation. While some people might like to use Atk/Spd Push 4 or Swift Sparrow, I still think Fury is better. With her tanky BST, all of her stats are important to her. Her decent defences of 42/31/27 allow her to easily tank hits from enemy attackers, usually with room to spare. However, I say "usually" because the occasional Lilina, Lysithea, Brammimond or Reinhardt can decimate her defences. Fury adds a much needed buffs to those defences, adds to her already solid offensive stats of 32/36 and can help her safely descend her Hp into the desired "strike" zone.

B Skill (Special Spiral 3): Special Spiral is an excellent infantry-exclusive skill; shortening the intervals between skills by 2 charges. Special Spiral is the reason I chose Luna to be her special. The 3 charges are shortened to 1, and during combat, as long as her desperation activates, and the opponent is not running a guard build, the second shot will always be a Luna.

C Skill (Distant Guard 3): This skill is entirely interchangable. I chose Distant Guard out of personal preference; I have a Legendary Edelgard build and I would like Norne to be able to support Edelgard while staying 2 spaces away. You can also run Waves for this slot, Infantry Pulse, or whatever you desire.

S Skill (Brazen Atk/Spd 3): I chose this seal to fix Norne's afforementioned poor Atk stat, while also allowing her to double even faster units. At just level 40, her Spd stat reaches an excellent 42, without supports, merges or dragonflowers. Reaching an unmerged Spd stat of 49 seems possibly unnecessary, but when you look at the other Brazen skills, this one looks a lot tastier. I know I said her defences are important, but after she reaches the "strike" zone of under 75%, her defences become trivial and all that matters is her offence.