Grand Hero Battle - Legion

The main purpose is to keep the Legions ALIVE with very little hp (because when you kill a Legion another one appears with more enemy units), so any member of the team can kill them with one hit, this can be done with Caeda.

The lancers and the blue mages should be easily killed with Camila, the legions (if not harmed) and the Brave Archer with Xander due to his high Def, and the sword and the Red Mage with B. Caeda and Azura.

Horse Emblem I know, but Olivia was the real MVP.
Give that dancer a Ruby Sword and Ax Breaker and watch her work. My Olivia didn't have an A slot or special. I imagine giving her +def, +hp, or TA will make clearing Infernal more smooth. I cleared Infernal btw, Olivia took out the majority of the ax dudes. Beast mode bae right here, no joke.

Lilina MUST have Axebreaker (axebreaker 1 is fine)
Nino also had B Tomebreaker

Engage first with Linde and Nino to bait the red and blue tomes, killing them in the next turn. Lilina will oneshot any Legion except the one with Aegis (which can be killed in oneshot only with a special skill).
You should always engage the attack and stay out of range (except the first turn). Take one hit and it's over. Use Olivia to move your units around after killing an enemy. Use colour advantage. Except for first turn, you must onehit every enemy.

The main highlight of this squad is Klein with Axebreaker to kill Legion easily. 2 Dancers with buff (hone atk and hone speed/ fortify res is recommended) to maximize Klein kill count. Nino is there to support the escape route, kill blue unit, or give klein hone attack buff if he's out of olivia range)

Ike with Axebreaker and Swap (mine's +spd -def so most natures work)
Nino with standard LnD Desperation kit (+spd nature is optional)
C skills Hone Atk & Hone Spd minimal requirement.

First turn have Nino slay both enemies to the right and have Ike move up to the top right corner of the defensive terrain. Make sure Ike's dancer ends the turn one step above bottom, same column as Ike. Don't break the wall.

Second turn have Nino kill the spawned blue mage and Ike Swap into his dancer then kill the spawned Legion.

Ike can slay the red mage with a dancer. Remaining enemies shouldn't pose much of a threat if you stay careful.

Infernal beaten on the turn the LnD blue mage cavalier spawned.