Maddening Fell Xenologue 6 3-Turn Strat

Maddening Fell Xenologue 6 3-turn
Translated from
https://gall.dcinside.com/mgallery/board/view/?id=fireemblem&no=551678&page=1
(Strategy not mine)

Character Builds

Alear (Female: Merrin personal)
Emblem Edelgard Lv 20
Liberation
Sword Power 5, Reprisal+

Framme
Alfonse S
HP +5 (survive the boss's 1st pattern for easier positioning)
Alear A Support (Hit +30, Avoid +5)

Saphir
Emblem Byleth
Alear A Support (Avoid +10)

Merrin
Emblem Chrom Lv 18
Rally Spectrum+

Seadall
Canter+

Yunaka
Emblem Veronica
Alear A Support (Avoid +10)
(Covert Contract grants Hit/Avoid +30 on top of refresh)

Veyle
Emblem Soren (editor: I think needs Lv 4+)
Excalibur

Alcryst
Draconic Hex
(Corrupted Wyvern combatant)

Etie
(Corrupted Wyvern combatant)

Madeline
Emblem Roy
(Blazing Lion, Hold Out)

Zelestia
Emblem Sigurd

Gregory
Emblem Celica
(Armored enemy combatant, right side Wyvern Knight combat with Warp Ragnarok)

Nel
Emblem Corrin
(Dragon Vein bot)

Damage Logistics
(1) Final boss has 24 AS, Liberation!Alear has 22 AS prior to attack speed modifications
Draconic Hex (24-4=20 AS) and Rally Spectrum+ (22+3=25 AS) allows Alear to double
(2) Final boss has 80 HP and 36 DEF + 50 Sigil Protection - 4 Draconic Hex = 82 PRT
(3) Assuming 1 HP on Alear,
17 STR
14 MT Liberation
15 Liberation Final Boss Bonus Damage
5 Emblem Edelgard STR Boost
7 Weapon Sync+
3 Rally Spectrum+
4 Instruct (Backup)
2 Spur Attack
10 Sword Power 5
19=39/2 Reprisal+
Total: 96 ATK
(96 ATK - 82 PRT) x2 = 28 damage
(4) Seadall and Veronica allows 2 more actions, so 84 damage per turn takes down a single 80-HP bar
Note that the boss initially only has 2 HP bars, so this only needs to be done twice.

Avoid Stacking on Alear

(1) Increase Speed and Luck with Rally Spectrum+
(2) Framme: Crimson Cheer +10, A Support +5
(3) Merrin: Knightly Escort +5
(4) Nel: Vein of Fog +30
(5) Yunaka: A Support +10
(6) Saphir: A Support +10 (may not always be available b/c of Seadall needing a space)
(7) Veyle: Anima Focus lowers boss hit by 20
(8) Draconic Hex lowers boss Dex and Luck
(9) (Yunaka's Contract temporarily grants +30)
All this lowers boss hit rate against alear below 50, keeping Alear relatively safe while her HP is 1

Strategy Breakdown

Turn 1
(1) Take down Corrupted Wyverns to left and upper right using Alcryst and Etie
(2) Alear just attacks the boss and chips around 30 of her own HP
(3) Seadall refreshes Alear, backs off appropriately
(4) Alear backs out of boss's attack range, the important thing is not to enter within 2 range of Seadall
(5) Merrin engages, equips Falchion and enters the range of the Wyvern Knight on the right. Can kill one on the counterattack
(6) Madeline engages and uses Blazing Lion on the armor on the upper left and creates fire tiles to prevent bow knights from rushing.
(7) Nel activates Vein of Flame on Alear, so that Alear has 1 HP on the next turn
(8) Take care of some of the armored enemies so that they don't enter the boss range
(9) Yunaka engages and summons a colorless. If you gacha summon a bow or a tome user, it becomes easier to to handle a wyvern knight enemy to the right on the next turn.

Turn 2
3 Wyvern Knights to the right
Merrin can counterattack one of them, so only 2 needs to be taken down
Cataclysm!Soren Veyle + Zelestia can take down one, Warp Ragnarok!Gregory + Summon Hero!Veronica can take down another

Use the damage and avoid setup explained above to take down one of the boss HP bar
The first avoid can be a bit shaky (~50 hit from the boss).

Turn 3
Ignore the boss spawning generics, repeat the damage and avoid setup to take down the 2nd boss HP bar.