In the builder its the one called shadow skills. A 40% chance to trigger the same skill a 2nd time for free. That said, its not really a 40% increase in bind chance. Say after all math you have a 60% chance of landing a bind. Shadow skills triggering a 2nd hit would make the overall chance of getting a bind more like 70%
Ah ok, after looking closer at the builder i assumed that was what he was talking about. I think i'm gonna go with the arcanist subclass because it offers more utility. Thanks for clearing it up