Torn Armor goes into detail about how their custom dice work for their game in their latest update on Kickstarter.
From the update:
I was asked to explain the dice in the game, so here it is:
There are 25 dice in the game. 5 sets of 5 different colors.
Dice have “hit sides” and “miss sides.” There is no “1,” “2,” “3,” etc. You either hit or miss with these and they have a custom hit marker (the shape of two swords crossing). If you see a blank side on the top, you missed, it’s as simple as that.