How to decrypt a WD MyBook drive after its removed from the enclosure?

In a nutshell, if you have a hardware encrypted My Book Model XYZ, and the enclosure fails, all you need to do is obtain the exact same enclosure from XYZ and insert the drive.

Hope this KBA helps clear things up regarding hardware encrypted My Books vs My Book with RAID and reading the drives on a regular PC
https://support.wdc.com/knowledgebase/answer.aspx?ID=15150