Patch 3.05 notes:

In addition to hunt marks, players can now obtain centurion seals by trading in 12 Atma crystals from FATEs in the new zones. These 12 atmas however must be attuned by completing the World of Darkness. Each clear will get you one point of attunement. A total of 150 points of attunement is needed per crystal. Once these 12 crystals are fully attuned, they can be traded with the hunt bill master for 1 centurion seal. Please look forward to it!