Each character class can select up to 3 passive skills that has nothing to do with or are independent of the 6 active skills (by default are assigned to 1 - 4 numeric keys and left & right mouse buttons).

[Edited several minutes later]
Note: Various passive skill options related to the character class are made available upon attaining higher levels.

This post has been edited by MOBAJOBG: Oct 15 2012, 03:52 PM