Talk:Gem Noir/@comment-93.47.216.136-20171221111627/@comment-26039274-20171222100418

Not exactly stack up, more like exponentially. And no, activating the same skill doesn't overwrite the first activation'seffect.

n = number of activation

For Gem Noir and if using 2 (or 2 activation of Gem Noir's skill), then the total buff is (100% + 100%)^2 = 400% ATK buff.