Wow!!, i just got an email from someone in Oracle to let me know that the Privilege Analysis feature of Database Vault has had its licensing changed from this week to now be free as part of an Enterprise Edition database (EE). This feature used to be a cost option and required a Database Vault license. To use privilege analysis you didn't actually need to enabled Database Vault but you needed the license. This is no longer the case from this week; Also i have been told that the licensing is also retroactive to all 12c versions.
The license details for 18c are here
I wrote an article back in 2015 and also did a webinar for SANS and Oracle on a practical walk-through of Database Vault and Oracle 12c and this included using and testing Privilege Analysis. You can read about that here
Great news; nice to see security features no longer being cost options. This is good to have; privilege analysis and reduction of privileges to least rights is also key to a super-locked Oracle database