Tips :
General :
The most important devices is : Single attack enhancement, defiance, special nail activation, all of that three enhancement, and soul weaver self increase combat readiness.
For elemental devices, focus on heroes that you will bring to clear the last floor. After that, heroes that you will use in the tower.
Make sure that you have many heroes or stigmas. If not, then don't let anyone of the main team be defeated.
Don't rely on buffs and debuffs too much, cause it can be easily dispelled
It is better to have big damage than landing many attacks, cause the enemies will take advantages of that.
For healing, it's better to use the one that based on max health not damage. Cause healing amount by damage will be decreased thanks to enemy's device. But if you want to increase survivability, then use both.
Third Period:
Cause in floor 25 there is Roana, don't have too many device that trigger a non normal attack. One is enough. Or if you still want that, then land unhealable and restrict debuffs on all enemies.
Floor 20 :
The most important point in clearing this floor is to not have too many non normal attacks. Except if you can overcome Roana's passive. Unhealable and restrict debuffs is needed to negate the effect.
Usually, in other two periods ( first and second ) i target the soul weaver hero first. But cause this time my fire elemental heroes are defeated already, i bring ice and dark elemental heroes instead. So, i target the fire elemental enemy first. Besides, Roana has revive buff in her third skill. Leaving her for the last make time for her cycling longer.