Canon Lady's effect is "decrease VIT (though more likely a poor translation of HP) by 12%." This means it decreases the total HP pool by 12%. If the enemy has 100,000 HP, she brings it down to 88,000. Since the game does not allow for excess HP, it immediately brings the boss down to 88,000. If you use it later in battle, such as 70,000 HP, the current HP is not exceeding the total HP, so there is no real impact.
A ha..
If so, summoning cannon lady first when attacking boss monsters will be efficent.
But I still wonder other debuffs and effects work or not.
When we use physical type character, STR increase physical damage, parry and accuracy, AGI increase critical hit, accuracy and dodge, and VIT increase HP, defense(?) and HP recovery rate.
So if physical type monster gets STR debuff, do their physical damage, parry and accuracy decrease?
I tested sometimes but I'm not sure exactly.. Decreasing 8% of STR looks no change.