ざくざくアクターズ - Ch 3. 手繰る魂のイリス

ざくざくアクターズ Chapter 3 - Secret Optional Ultra Hard Hidden Boss.
No chessy strategy used. Straight up fight.
This boss (Her name is Iris) is somewhat hard if you don't cheese it. All characters had 45% Mitigate Frost damage going into the fight.
Beating the girl down is the main objective. The spear behind, as indicated by the name, is invincible.
Every 7 rounds, she will cast an ice ability that does massive damage and puts all frontline players to sleep. Players immune to sleep or equipped with immunity to sleep was used to soak it. The turn right after, she rests, heals for 6-7k, and takes 3x more damage. Can cheese here if done right
The spear will attack 4 times in one round once every four rounds.
At 20% health, she absorbs the spear along with its ability.
After beating her, there is an even harder version of her with more health, stats, and most importantly, you have to deal with the spear, and her with the absorbed spear ability from 100% to 0%. That ability alone is what makes the fight insanely difficult. I haven't beaten that one yet.