Grand Hero Battle - Clarisse

Link: https://youtu.be/GmyEuHkKxik?t=5m09s
Ninian: +SPD -ATK
Iceberg, Scape route, Fort Def
Celica +1: +ATK -RES
L&D 2, Seal Res, Spur Def, Reposition, Moonbow
Olivia: Neutral
NO SI
Sharena: Neutral
Reciprocal Aid, Moonbow, Darting Blow, Drag Back, Fort Def

Henry can tank not only the intial hit from Clarisse and the ninja, but if you send Henry up to the defense tile and have all the greys dead (Henry and Sonya together can take the greys out by the end of turn 2), henry can tank all the remaining units, besides the wo doa user that nephenee will be fighting at the right choke. Henry will be at critical health thanks to the blue mage (yes he survives even with triangle adept, I’m surprised too), genny can heal him and you can just take out everyone else from there with Sonya, nephenee, and Henry
Edit: Sonya with blue tome breaker helps. Like a lot. I got screwed over by panic and hone speed on genny, so using blue tome breaker to kill the blue mage helps, so if you really want to you can switch Sonya with fem*robin, or just give her the skill

Just use the 2 BK's and destroy the entire map.

Robin is really the star of the show, being able to tank hits from both Clarisse and the thief. As long as you keep him away from the green mage, he'll be fine. Make sure he is running TA and slap the Fortify Res seal on him. Azura and Lucina should be running Fury. Azura also had Hone Atk. Elise should obviously have Rehabilitate.

Position them with Robin in the rightmost square, then Azura, then Lucina, and finally Elise in the leftmost square.

Send Robin up to the first space where he can be hit along the edge of the map and keep the others in their starting positions to avoid being debuffed by the thief when he attacks. On the next turn, move Robin down to the space beside the two pillars to take out the red infantry unit and then sing him to safety (corner) without moving Azura. Move Elise to the bottom rightmost space and position Lucina above her.

The green mage will attack Azura, so make sure you're running Fury on her and the Fortify Res seal on Robin. Mine survived with 1 HP (total HP 40, total res with buffs 33). Kill the green mage with Lucina, move Azura next to Lucina (above Elise), and use Elise to heal Azura. Move Lucina to the other side of Azura so that she's in the crook of the backwards L wall. Move Robin above Lucina.

In the next turn, kill the thief with Lucina. Move Robin above her to kill the red cavalry. Sing to Lucina and move her clear of Clarisse. Heal Azura with Elise again.

Clarisse will attack Robin, do no damage, and die from it. Move Robin clear of the final blue mage and Lucina to the space below the edge of his range. Heal Robin with Elise and leave Azura where she is.

Finally, move Lucina onto the defensive tile and attack the blue mage. Use Azura to sing to her. Attack and kill him.

(This team had Goad Cavalry and Hone Cavalry buffs.) I don't have Xander, so I used Leo instead. Use Leo to bait the dagger user and green cavalry mage from the bottom left tile. He should be able to tank both hits. Fyi with this team, if you start the battle virtually any other way, you're much more likely to lose.

Finish off the green cavalry mage then use Azura to get everyone out of attacking distance. In the next round, use Camus to attack Clarisse, then bring Reinhardt in for the kill. Use Dance on Camus so he can finish off the dagger user. Camus should be able to tank the hits from the reds. Use Leo and Reinhardt to finish off the reds, then use Camus to kill the blue mage.