IMO, the +mana stacks should be reduced by 5%, not clear them all and -5%.
My magic heroes can compensate for the -5% mana stack by using special skills and giving a 5% mana stack to a random hero.
If this applies, why the bosss clear all the mana stack before adding a -5% stack??
I should have posted this earlier but better late than never.
The magic family mana stacks don’t interact very well between the positive and negative stacks, I think it should be the case that a negative stack should substract from a positive, for example if you have a +10 mana stack and the enemy tries to put an ailment of -1 or +1 negative stack it should be substracted, nos substituted. In the screenshot I have a team of heroes with a 1 in negative mana producion stack but 1 hero still has a 10 in the positive stack because the enemy missed the attack, the rest of the team also had a high positive stack because of my multiple magic family member setup but my whole positive stack was removed and left with 1 negative.