From publisher blurb:
Clerics of the Marked Guardian Domain have been anointed and sworn to protect a history lost to the world. Forced to forsake the outside world either by birthright or by joining those who would guard these ancient secrets, you have had this history marked upon your body, either through ceremonial tattoos or bloodletting, and shared it only through oral tradition.
Building off of the existing Fifth Edition rules to build a cleric character, the Marked Guardian Domain gives you options to build an enigmatic cleric, a member of a secret society who bears the records of a lost history in tattoos and markings.