Nathaniel Peters, from Martian Dreams
Nathaniel Peters was the gatekeeper of the human settlement of Olympus on Mars. When the Avatar first approached him in Martian Dreams, Nathaniel would not let the hero's group pass, under orders from Jack Segal, their settlement having had too many incidents with the "loonies from Elysium." In order for them to be allowed in, Nathaniel required the signatures of three individuals whose character was known to the dwellers of Olympus, and whose soundness of mind was certain. Lt. Dibbs' signature was considered invalid, as he had not been to the settlement in weeks.
On Dibbs' suggestion, however, the group sought out the trio of explorers Richard Sherman, Dr. David Yellin and Major Greg Duprey, the signatures of whom Nathaniel said would be sufficient to let the Avatar and companions inside. After locating and assisting them with their own dilemma, the three gladly vouched for the Avatar, gaining them entry into Olympus at last.