Beat Infernal with Nino, Azura, Bridelia, and Ike. It took me two Stamina potions worth of attempts to beat this.
I've been using +SPD/-ATK Ike without much issue in the Arena, but I hated not being able to activate Heavy Blade even with the ATK+3 seal. If I had just neutral Attack, I would have been able to activate Aether more often with the ATK+3 seal on. So I had to stick with Fury 3 as usual, but Vantage 3 came in handy very often.
I relied on Nino to take out the Knights, and Bridelia just shot down tons of other enemies. I actually switched to Escape Route 3 just for this map, and it was worth it. WoM3 dancing is also very crucial here. It got pretty hairy toward the end, but I took out Arvis and a few southern reinforcements on the same turn.