Bound Hero Battle: Alm & Celica

Not exactly easy to get units, but if you happen to have them, this worked for me.

Ike (+ATK, -RES) Skills literally don't matter at all. He doesn't even need distant counter. He can likely be replaced with any decently tanky sword unit as all he does is (almost) kill the green mage and tank one hit from Alm.

Frederick (+ATK, -RES) Brave Axe (Mine doesn't have +), Luna, A slot doesn't matter (mine is just HP 1 lol), Drag Back (this one is important), hone attack 2 (this isn't really necessary, but have some kind of hone skill on him, even his native fortify cavalry, at least), reposition (also important), and fortify res seal (Not mandatory, but helps Olivia tank the green mage, and provides a small buff to Mae). Pretty common/easy unit to get.

Olivia - Mine was a lvl 35 4*, and I don't know what her IVs are. If you have a lvl 40 one though, you should be good to go. She should be able to tank 2 hits from the green mage. Skills don't really matter (except dance of course, and hone attack is always nice). Free to play and easy to get.

Mae (+SPD, -DEF) Blade Tome (not +), Darting Blow 3, Desperation (These skills may or may not be necessary). Replacements may include other standard blade tome users, powerful and preferably fast raven tome users, or Reinhardt.

Turn 1: Position (from left to right) Ike, Frederick, Olivia, Mae. Have Ike move up 1 and break the wall. Have Olivia go up to his right and dance. Move Ike down. Move Mae up and right to the corner at the wall. Leave Frederick where he is.
(Enemy Phase: The green mage should attack Olivia, and units should start coming down.)

Turn 2: Kill the blue mage with Frederick. Move Ike one space right. Move Olivia to where Ike was, and dance for Frederick. Move Frederick right, parking next to Mae. Leave Mae where she is.
(Enemy Phase: The green mage should attack Olivia once more. Alm should come down behind the green mage with Celica next to him. The green axe flier and lance cavalier should both attack Frederick, which Frederick will be able to easily tank. Keep in mind the lance cavalier has pass so he should end up to Frederick's left.)

Turn 3: Kill the green flier with Frederick. Drag back should put him out of reach of Celica. Move Mae up and left onto the defensive tile and kill the lance cavalier. Here is where we take advantage of stupid AI. Move Olivia 2 spaces right. Move Ike up to the green mage and shank him. It shouldn't kill, but severely wound the mage.
(Enemy Phase: Celica should attack Mae, which Mae should be able to tank fairly easily. This will ready Mae's dragon fang. The green mage should run away, and Alm should attack Ike.)

Turn 4: Kill Celica with Mae. Move Ike 2 spaces right. Move Frederick up 1 space and reposition Ike to the other side of him. Then, dance for Frederick with Olivia, and use him to kill the green mage. Once again, drag back should put him out of the range of Alm.
(Enemy Phase: Alm should be the only enemy left. He will start moving closer to your units.)

Turn 5: At this point, it's GG unless you royally fuck up. Just play around with dance and positioning skills to get a nice setup, buff Mae, and nuke the shit out of Alm. EZ enjoy your 4 orbs.

(Disclaimer: even though this should work, I don't guarantee success as small differences may cause small differences in AI decisions.)

All 5*'s, Level 40's

Lady of the Lake - Azura
LV.40+4
HP 45
ATK 40
SPD 30
DEF 22
RES 30
Brave Lance + / Sing / Moonbow
A-HP+4 / B-Wings of Mercy 3 / C-Hone ATK 2
Sacred Seal - HP+3

Thunder's Fist - Reinhardt
LV.40+1
HP 39
ATK 45
SPD 18
DEF 23
RES 25

Dire Thunder / Draw Back / Luna
A-Death Blow 3 / B-Lanceb.3 / C-Threaten Res 3
Sacred Seal - Quickened Pulse

Dark Shadow - Tharja
LV.40
HP 39
ATK 48
SPD 35
DEF 23
RES 17
Rauorblade+ / NA / Retribution
A-Darting Blow 3 / B-G Tomeb 3/ C-None
Sacred Seal - Speed +1

Naga's Blood - Julia
LV.40
HP 34
ATK 50
SPD 26
DEF 20
RES 32
Naga / Rally Attack / Dragon Gaze
A-T.Adept 3 / B-L.breaker 1/ C-Breath Of Life 3
Sacred Seal - Attack +1

How to use the team
Turn 1

Have Tharja go into the range of the green mage on the far right tile of its range. Below Tharja, use Rally attack, and have Reinhadrt on the right of Julia, With Azura on the left. The Green mage will kill itself againt Tharja, and every unit moves down.

Turn 2

With Julia, kill the Lance Cavalier on the right side, then have Reinhdarth use Draw Back to get her out of the range of the Axe pegasus. Use Tharja to attack the Axe knight, then have Azura use sing and have tharja move all the way to the right.

Turn 3
Have Julia go all the way to left and attack the blue mage. Have Azura use sing right on the right of her, and move Julia to the left to bring her out of range of the flier and kill the blue mage. With Tharja, have her block Reinhart, and attack the flier so he doesn't get ORKO'd by the Flier.

Turn 4

On Turn 3's Enemy phase, Alm should have ran down and attacked Tharja, leaving her at 3 HP. Have Reinhart ORKO Alm, and have Tharja kill the flier. With Azura, use Sing on Reinhart and have him ORKO Celica.

TLDR:
Bait out Green mage with Tharja, Kill both blues with Julia, Have Tharja clean up the green unit, and Reinhardt ORKO both Alm and Celica.

The first step is to lure the green mage with Cecilia, placing her just beneath the breakable wall (do not break it yet). Xander is at left side and Camus waits below her.
The blue cavalier will break the wall and they are finally exposed, finish the green mage with Cecilia and push Camus to kill the blue, Camus received Fortify Cavalry from Cecilia to be able to withstand Celica's Ragnarok and some hits from Alm. And within that turn Ninian danced Cecilia to blast off the Mounted Lancer.
Camus will be heavily injured by the Bound Heroes but he is ready to finish Celica off her marks, after that I pushed Xander to reposition Camus back and Xander is right in the Def. tile to deal with Axe flier and Alm quite easily.

IVs
Nino: +SPD/-DEF
Priscilla: +ATK/-DEF(doesn't matter really)
Xander and Camus: Neutral
(Skills are in the video)
Didn't really have to use any fancy units for this, but here's an overview:

Xander's sky-high defense allows him to take hits and with QR 2/3, he can charge his special, Ignis, much faster. Camus' job is to finish off the blue mage, Alm, and body Celica; however, his resistance is lacking which is why Priscilla was chosen. Priscilla was there to heal, provide Xander with 6 extra DEF thanks to Spur Def 3 and Spur Def seal, and also provide the team with +4 Res which allows Camus to survive Celica's attacks. Finally, Nino is just here for the green mage and to damage Alm, though my Nino does have Sparrow Strike 2 so killing the green mage would be difficult without it.

Best to watch the video to fully know placements(recommended to follow step by step)
https://youtu.be/VtY2fP_ByuQ

Ryoma here is the saving grace. With his high speed and attack, he's a good counter to Celica but ONLY will this work if you can time astra with it so he can OHKO her. Shanna can also take a hit from Celica from the wall, she's not very good at countering Alm. But she does kill the other enemies decently with quad attack with a brave lance. Sakura rehabilitates everyone, and Nino is an extra drag back, you'll need it. The only 5* is Ryoma, everyone is is 4*

1. Start on the left and lead with Shanna, have Ryoma drag her back
2. Let Shanna take the hit, then let Ryoma kill the enemy in front of her, then have Shanna kill the horseman to the right.
3. From what I can remember, Ryoma will kill most units while Shanna stalls the mages.
4. Towards the end, if all goes well you should have Ryoma and the rest of the team out of range, when she steps forward and you have Astra charged, you should be able to kill her instantly. (Sorry for bad explanation, I can hardly remember what exactly I did).