Shamshir Naik is many things; he is the oldest Trinity known to be alive, a very intelligent and learned man, a manipulator and puller of strings, a trickster and sneak to some even. He is also a man with a heart of gold.
Since the day he met Alexander on the banks of the Hydaspes river in BE27, Sham has tried to do what is best for the people he loves. He is not always successful and, at times - he will be the first to admit - his schemes do go disastrously wrong. He is indirectly responsible for the Council and the rise of Ataraxias, later known as Prefect Apatèon of the Union.
Perhaps this is the reason he will not speak of Unity. He was the only person with her and perhaps feels he missed his one chance of redemption.
Sham was encouraged to meet Alexander by a mysterious being that took the shape of a old Indian sadhu but was able to appear as it pleased and, Sham suspects, sometimes takes the form of the small black snake he affectionately calls "Nag". It was he, not Sham, that healed Alexander in Babylon. It was he, Sham believes, that directed Gabriel and Unity to his house in India. Nobody, especially not Sham, has any idea just what that being is or what it wants but we owe the shape of our world as it is to now to its actions.
Though nobody would believe him, Sham can honestly - and quite rightly to some degree - claim be a pawn and the manipulated rather than the manipulator he is seen to be.
He is also, he will shamelessly tell anyone, a coward.
He vanished from the Palace in Alexandria and was thought dead by Alexander and his friends because he was afraid that they would become aware of his refusal to age and think less of him.