⇊ Units used, details & music (Please read before asking anything!) ⇊
Sorry for taking so long, hope these solutions help.
Remember that the first one is ONLY for Infernal difficulty, the other two are for Lunatic.
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Note: Remember that they can be different units, as long as they are able to serve the same purpose.
---------- Infernal Solution: ----------
-[Slot 2] A melee unit with at least 2 movement:
-Weapon: Any
-B: Wings of Mercy / Escape Route (A cavalry unit can't use Escape Route)
If you're using Escape Route, this unit needs to get in range from a battle with Legault.
-[Slot 8] A 2-range cavalry unit:
-Weapon: Any
This unit needs to get on WoM range from a battle with Leo.
-I used a 4★ Picnic Leo with at least 5 extra speed.
-[Slot 3] A dancer or equivalent:
-Assist: Dance or equivalent
-B: Wings of Mercy
---------- Lunatic Solution: ----------
-[Slot 1] 2-range cavalry unit:
-Weapon: Any
-B: Wings of Mercy / Escape Route (depends on your setup)
-I used a 4★ Rolf:
-Weapon: Candlewax Bow
-B WoM / Escape Route (both work)
-[Slot 8] 2-range cavalry unit:
-Weapon: Any
-B: Wings of Mercy / Escape Route (depends on your setup)
-I used a 4★ Picnic Leo:
-Weapon: Wind
-B: WoM / Escape Route (Both work)
-An extra 5 speed or more.
-[Slot 6] A melee cavalry unit:
-Weapon: Any
-B: Pass
It doesn't matter if this unit doesn't get on WoM range, as long as the other units both have Escape Route, if one or both of them have WoM, this unit will need to get on its range, as well as staying on Pass range.
-[Slot 3] Any melee unit:
-Weapon: Any
---------- Galeforce Solution: ----------
-[Slot 6] Brave Roy:
-Weapon: Blazing Durandal (with special refine)
-Special: Galeforce
He needs to get on WoM range.
Yours might get killed since mine is +Def, in that case you can equip him with Steady Blow or anything that can help with his defense.
-[Slots 2 & 5] Two 2-ranged units (movement type doesn't matter):
-Weapon: Any
-B: Wings of Mercy
-The other units are the ones that you want to farm HM, they must be level 40 (to get max HM) and have nothing equipped (and I mean nothing, unless needed).
Make sure that none of the units have assists or Pass, unless needed for the solution to work, in that case, equip them on the units that I point out (Assists change movement order & Pass changes where they will move, even if they don't use it at all).
Also make sure none of your units kill an enemy on Turn 1, that will cause a new enemy to spawn on Turn 2.
Glosary:
WoM = Wings of Mercy
ER = Escape Route
HP = Health/Hith Points (I'm not sure which one is it kek)
SS = Sacred Seal
HM = Hero Merit (Each 500 you get 500 feathers, this is the reason these guides exist)
If you have any questions, feel free to ask, I'll do what I can to help.
You can check on this later if you're having trouble, as I'm constantly updating it if needed.
Music used:
Earthbound OST - Pokey Means Business!
www.youtube.com/watch?v=QLR4mnndnj0&list=PLfBkxe4qFTd7_ae0ECqxYRRyJA_xK0OvK
Thanks for watching!