The reason why lvl 12 is made to be very difficult is that you may get seal scrolls from it, and also a higher probability of getting a 3 star ninja, along with the fact that if you pass all 12 lvls, you'll be able to sweep up to lvl 9, leaving you with only 3 lvls that you need to clear.
I suggest you to save at least two full teams with full health for the last lvl,
if you see your team has almost been completely defeated, you c*ways retreat and try again with full health. Especially for the last 1 or 2, you may need to try a few times, so please don't use auto.
Another thing is, you should choose your ninjas for each round with reference to the strengths and weaknesses of your opponent, such that having a medic on your team when facing a team w/ conditions and controls, hinata or neji when you are facing a lightning etc.
This post was last edited by moumin at 2016-8-5 06:40