What the actual..

I haven’t managed to beat it yet either. Just waiting for PM1, Lu Bu, or Omni to post some sort of guide. The map is hella hard.

These LHBs are generally a bit ridiculous, but as you're seeing, she can potentially strike as far as a melee horse assisted by a dancer, seven squares from her position at the start of a turn. It's a very tricky assist.

I did beat it, although it's difficult to give any advice. As soon as I saw that defensive tile at the top of the map, I knew that it's the key to my victory, so I killed that green cav with Lilina and rushed Nowi closer to the defensive tile. She got there by turn 2 and it was smooth sailing from that point onwards.

Yeah I did it in about 3 tries but I used a heavyly invested Dragon Emblem team and a healer

Yeah I did it in about 3 tries but I used a heavyly invested Dragon Emblem team and a healer

Completed the map with Reinhardt, BB LA!Row and 2 dancers.

Rein (or Ishtar, I used Rein for ease of use though), LHectr (avoids doubles and Lucina cant kill him easily), A!Tiki with a Breath of Fog set and aether (healing with aether and her weapon was pivotal for me) and P!Olivia with Chill Atk, to mitigate as much damage as humanly possible. Alot of repositioning and keeping track of where and how Lucina can move. I'm more worried for Arena when she becomes a common unit...

Found a clear, but it's very difficult. I used +atk L.Hector (important for one-rounding certain opponents), Nowi+4 summoner supported +spd -res, Marth with buffing Falchion + spur spd + drive atk 1 ally supported to Nowi , and Sothe (base kit, no offensive boon stat). Hector did some enemy phase work on the left, we waited for the green cavalier mage to come in, busted him with one hit from Nowi and one from Sothe, which gave Nowi ridiculous stats, and then I sent Marth in just to buff Nowi even more. She was directly in range of Lucina, so Lucina went straight for her. Nowi was able to get an aether off on Lucina while blocking a double, so Lucina lost that quite badly in one round. The rest was cleanup.

I used cancer duo (B! Lyn and the Reinhardt), E! Chrom and PA Azura
Took me a few tries (man that future vision move is annoying as fk) but I eventually got it

B!Lyn + 3 dancer cheese beat it for me. PA!Azura tanked Lucina’s shot though, and she needed TA, spur speed, hone speed, speed +3 seal, +spd iv, and two merges

Desperation Nino did most of the job for me because Lucina sometimes would kill my L!Ike.

My team: +7 Nino, Ninian, F2P L!Ike, F2P Fjorm

Beat it with Camilla Emblem. A heavily invested Vanilla Camilla (+10, Distant Counter, Aether) and a typical Raven+TA Spring Camilla were the stars of my run.

Getting around Future Vision was quite tricky, but managed to bait her into the most ideal counter (Spring Camilla).

I was forced to use my main team to beat it.
a
A!tiki, nowi, nino (all+10 fully built) and axura.
The only advice i can give is to take a green that can bait both magic and physical attacks, cause you will have to bait lucina and are most likely going to take a magic hit or two on the same turn in the process.
Having aether really helps too.

I beat it with:
Atiki +10 LB, Aether, WB, QR2, Atk smoke 3, CD 3
Shenna + 7 Slay axe, Aether, DC, VF, Atk ploy
Genny Gravity Dazzle, atk3, Wrath staff, Savage blow, Def Tactic
Lute OG Set with desperation, and Res tactic.

Atiki bait in the left and Shenna bait in the right in the first turn, then the enemies kill themselves.

It was rough, but I've been able to clear the map with Nowi (+9), Tiki Adult (+9), Fae (+6) and Bridal Lyn. Basically, my core Arena team and a healer.