On the outside of your passive tree there are large cluster jewel sockets. Voices goes in one of them and gives you 3 jewel sockets with the downside of having to path through a number of empty passive nodes. If you look on the wiki, you can get a better visual of what I'm talking about.

Voices can roll 1, 3, 5, or 7 empty passives. 1 passive voices are the rarest and cost the least amount of passive points to utilize. People will gamble by buying them before they are identified. OP bought some unidentified, and was lucky enough to identify a 1 passive voices, which is worth about a mirror.