I've killed 4 of the 5 cultists and the sage on the Worshippers of the Bloodline branch of the cult. The last cultist in the branch is still an "Undiscovered Cultist" (shown as a cult mask), with the hint
Hunt other Cultists from the same branch to gain a Clue about this Cultist's identity.
There are no other Cultists in the branch left to hunt (sage included). Did I miss the Clue that unlocks this cultist? Can I go back and find it somewhere?
The cultist I'm missing is the far right end of the lower branch of the Worshippers of the Bloodline. On that branch I've killed
Zoisme, Harpalos, Diona, Melite, and the sage Iokaste