I meant that they stack as in, if you have 1 Aleph Mask and 2 Gemini Mask, you start with the base 40% from Gemini Mask, and you add 5% for the second Gemini Mask and then you add 5% for the Aleph Mask, for a total of 50%.
The 86% is a relic from when the masks' base percentages were 33% and 66%; it should say "60%" in that place.
So, if you have some of each, you start from Gemini's 40%, then add 5% for each Gemini after the first and each Alpha (for a maximum chance of 95%, in the highly unlikely case of having 6 of each)?
How'd you get 95%?? Seeing as they're the same card, just that Gemini is the upgraded version, you can only have 6; 40% for the initial mask, and 5*5% for the other mask, that's a total of (40% + 25%) 65% isn't it? o_O Even then, when will you draw all six cards? I have 6 Phase Shields (Aether FTW!! Non-Phase Shield decks are really fun too =P) and they usually take a good chunk of the 24 turns to bring them out.
Assuming you have 6 Geminis, and assuming an optimal draw (1 gemini on the first turn) where every one but the first played is duplicated, we get (chance to duplicate the card drawn AFTER Mask number):
1) 40%
2) 50%
3) 60%
4) 70%
5) 80%
6) 90%
The total odds of duplicating 5 geminis in a row (assuming we draw at most one in the opening hand otherwise it is impossible) is 6.72%. This is pretty likely in the scheme of things. It's unlikely however that it would happen in a real situation, where you have the quite likely possibility that you draw more than one in the opening hand (particularly if you go second, or you have only ~30 cards), and the additional complications of enemies destroying/stealing your masks, not having enough quanta to play one of the 11 masks involved (77 over the course of the game) and the game ending before you get the chance to play them.
So, basically, it seems like a nice addition to aether, continuing the duplication theme.