[SPOILER] Alexander von Brennenburg...

[Alardem]

From what I understand, Herbert was one of Alexander's contacts who were involved with finding artifacts. Daniel happened to be part of Herbert's archaeological expedition, and it's when Daniel finds Herbert's list of contacts that he managed to meet Alexander.

Also, Justine's family is implied to be part of this same order of aristocrats - Daniel's letter was sent to Justine's father around the same time he was murdered, and Justine is hinted to be aware of the Orb's existence.

IMO, this Illuminati-like cabal of paranormal obsessives eventually gave way to the Archaic caste whose corpses we find in Penumbra: Black Plague.