As the title suggests will decrease attack stack with the 50% decrease attack debuff and will they end up at a 80% reduction?

As I happen to have him I wanted to make a cb team that would last a long time since my dmg comes from poisons (mainly) hence extra turns will be a blessing to reach that 1 key. If anyone has tested this It will be much appreciated since I dont want to end up wasting resources even though he looks cool :) I tried to find the answer but the content creators usually focus on arena which might be the wrong spot for him https://100001.onl/  .