Theorycrafting with Ryu: Selena

She was the first to be desired and I had already sort of figured this out while at work, but I have 2 votes for Sheena and Michealis to do after this so I might do one of them after I'm done with this depending on who you guys have/like more.
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Selena
+Atk/-HP
Slaying Edge+/Killing Edge+
Reposition
Bonfire
Fury 3
Vantage 3
Defense Ploy 3/Threaten Defense 3
HP +3 seal/Quickened Pulse
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Now, I came up with this build when I looked at her stats and Selena reminded me of my Summer Robin. Both are very good hybrid tanks and have decent speed stats and average attacks at the cost of health. Selena is however physically tougher at the cost of 1 resistance and a bit of attack which is ok because she gains a whopping 4 back with an attack boon.

Below is the final results of her stats with this build:
HP: 37
Atk: 46
Spd: 38
Def: 35
Res: 31

With this spread, she becomes a tough duelist tank that can handle both mages and melee threats of the green and red varieties quite well. Even a speed boon Fury using, +1 spd seal Nino requires 2 stat buffs (assuming 1 is attack) to kill Selena in a single round by doubling her. Blade Leo must be given Hone cavalry (Fortify isnt enough) in order to kill her in a single shot and Thajra(or other equal speed red mages) needs a speed boon and to keep her darting blow to land the double attack to kill her as well. the only green mage that is a more common threat is Cecillia who with all Cavalry buffs, deathblow and attack boon only just perfectly manages to 1 shot this Selena unbuffed due to her HP bane.

In melee, she will be able to attack the much slower common vantage users safely as once both enter Vantage range, she need only let them attack her first. In regards to Takumi, her massive defense usually means he is a non issue for her. Unless he is defense boon, Hector cannot last a full round against her. Xander is a draw unfortunately regardless of who attacks first unless Defense Ploy or Threaten Defense has triggered, then he will due attacking into her Vantage attack. Ike is actually easier so long as Swordbreaker is not kept (it is usually traded for QR or Vantage anyways) and he can be safely defeated in a single round on attack or bait.

An important tank target is Bridal Cordelia. Even built for quad strikes, unbuffed Cordelia fails to hit more than 2 times with her Brave Bow and even with an attack boon, seal and deathblow 3, she cannot ohko Selena and will die to a charged Bonfire or even a neutral attack (if she was using L&D).

Ryouma cannot hope to double strike to kill her without a speed boon and L&D, and Lucina has the same issue unless she is Fury 3, speed boon and speed seal.

In short, she is built here to function as a solid hybrid damage tank (she's on the high end for physical actually) and she can avoid being doubled by most enemies she faces by just barely being high enough that it has to be a severe tryhard speed build which usually ends up with the use of L&D and squishy targets for her and your allies that you choose to support her. Against targets she doubles (and fails to kill) or 1 round draw fights against, she will usually destroy with her vantage charged Bonfire adding 17 extra damage to her attack as a massive power spike. You can toss a Quickened Pulse seal for some bursty bait and burn combos or put her with someone running Infantry Pulse to trigger the special even more often!
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~Previous Theorycrafts~

Hawkeye: https://fireemblem.gamepress.gg/q-a/theorycrafting-ryu-hawkeye

Caeda: https://fireemblem.gamepress.gg/q-a/theorycrafting-ryu-caeda

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Feel free to request next heroes for theorycrafting but atm it seems Sheena is winning that poll.