Just wanna share some info on how i cleared the more challenging trials (aka 15 rounds and Not losing units). Maybe it may work for you as well?
For "Clear in 15 rounds or lesser", i brought a total of 3 units namely, 2 Seraphina (ownself + friend) and a Maelos (got no other swapping units).
PS : I didn't bring any more units cos i didn't want the friend unit to be spawning at other grids.
For the "1st wave", just clear them as per normal, don't waste your turns here waiting for cd thou !
For the "2nd wave", you can choose to just "end turn" or maybe kill 1 or 2 chest (which can help reduce the damage you received). This is the best wave to wait for your skill cd, Since you'll definitely waste a few turns here.
Note : For "2nd wave", if you're bringing your full team, don't delay the skills of the chest thou, it'll do you more harm !
Now come the "3rd wave". You'll want to "pull" the boss unit to the front of you (in this case i used Maleos). Now that Maleos has done it's job, let it die so you can trigger the friend summon, meanwhile have your own seraphina attacking the boss. Just rinse and repeat the attacking and you should be able to clear the trial.
Ps : Took me exactly 15 turns, but maybe because i only have 2 units attacking at once. Maybe i'll try with a full team and let you know again?
For "Clear without losing any unit" , i brought as per usual, 2 Seraphina (ownself + friend) and a bug. Yeah, a bug. Just using it to trigger the friend summon. Also, you might want to bring some healing items just incase (didn't use any thou).
For the "1st wave", just clear them as per normal. Personally i let my bug die here, just to get your friend's seraphina out. Which will make things easier.
For the "2nd wave", try to clear as many chest as you can. Hopefully you get the one with the rewards.
For the "3rd wave", just attack the mobs and it should net you your clear.
Ps : For this trial, i realize that have 1 unit to die and then triggering your friend's summon, DOESN'T count as losing a unit. I know, weird.
So hopefully this will help those who are having problems in clearing. Personally these 2 trials took me a few tries before clearing them. At some point in time, it boils down to luck and RNG. I wish those who are gonna try it, all the best and good luck !
