Board Thread:Questions and Answers/@comment-25769372-20150725040933/@comment-1050617-20150829092857

Uh oh, trying it with only 4 stars is clearly a risk. I suggest try 30% HP boost for your leader and the same with your friend. A mitigator with great Def Buff can also help.

I suggest a 7* Griel for Friend since her LS boosts HP and Negates all ailments (If you're trying the Thunder Mecha that is)