Signature Ability

Each career (not specialization) has two signature abilities; these can be found in the career book for that career (so the Explorer signature abilities are in Enter the Unknown, for example).

They basically act like a super talent with upgrades, and you 'attach' them to the end of an in-career specialization tree.

To get your second signature ability you need to meet the prerequisite talents the Signature Ability links to.

Unless the GM allows it, they can only be taken by the career they are made for.

If the career book has not been released, that career doesn't have any signature abilities.