Units (all neutral IV except Stahl who is +HP -Spd)
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4* Gunter w/ Reciprocal Aid inherited, and Drive Atk 2 seal (you might be able to make do with Drive Atk 1 seal)
4* Cecilia w/ Atk+1 seal
4* Camus w/ Spd+3 seal
4* Stahl w/ Quick Riposte 3 seal (Quick Riposte 1 should suffice)
My Stahl is +HP -Spd because I foddered off my neutral ones when I was a newbie (mistakes were made). To my knowledge it shouldn't affect this approach, but I have no way to test if the AI will behave in the same way until I get another.
You might be able make do with Spd+1 seal if you have ally support between Cecilia and Camus.
This was something I've tried some time ago, and I was hoping I'd reacquire an IV neutral Stahl before recording it. But, months of rolling later, my newbie mistake continue to haunt me. As the Elite quests are ending soonish, I thought I'd share this in case it might be of use to someone.
Turn Summary
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Turn 1: This turn was used to position units so Cecilia and Stahl get Hone Cavalry, and Camus's Goad reaches the tiile Cecilia will attack from.
Turn 2: Cecilia attacks the Green Axe Infantry, and Stahl moves her away using Swap. Stahl's Obstruct prevents the Green Axe Infantry from attacking Cecilia, and his Quick Riposte will take out the Green Axe Infantry if they attacked Stahl. The enemy instead will attack Cecilia with The Cavalry Archer, but doing so blocks prevents the green Axe Infantry from moving foward, and hold back the other units at the back.
Gunter is moved so Camus gets Hone Cavalry buff next turn - he needs that extra Spd.
Turn 3: Cecilia takes out the weakened Cavalry Archer, and Stahl uses Swap to move her back. The Green Axe can attack Stahl, and with Lunge move him into the range of the other units at the back. Quick Riposte allows Stahl to take out the enemy so he can't be lunged.
Gunter uses Reciprocal Aid to transfer his HP over to Cecilia. This will be needed later.
Camus moves back but remains in range of the Green Axe Flier. He takes more damage than Stahl in a battle, so the Green Axe Flier will go after Camus. The Spd+3 on top og Hone Cavalry prevents Camus from taking a follow-up attack.
Turn 4: With the Green Axe Flier so far behind enemy line, Stahl mvoes to take them out. The others position to take on the remaining 3 enemies. Stahl isn't going to engage anymore, and Gunter takes his HP so they can be transferred to Camus next turn.
Turn 5: Gunter transfers his HP over to Camus, and between Hone Cavalry, Drive Atk and Goad Cavalry, Cecilia can take out the Blue Lance Cavalry. Stahl then uses Swap to move Cecilia into range of the Blue Mage. This is needed to allow Cecilia to take out the Blue Mage in the player phase. The Blue mage is faster than Cecilia, but Wind Sweep means that if the user intiates combat, they cannot get a follow-up attack.
If you have a Drive Atk 1 seal, move Camus below Cecilia, so she gets extra Atk from Goad.
Turn 6: Camus is moved up to block off Lloyd, and in doing so puts Cecilia within Goad Cavalry range. With that she can take out the weakened Blue Mage.
Turn 7: Camus takes out Lloyd with help from his Special.