A few words of explanation may be in order, since initial comments on the
story requested clarifications:
Brigadier Alistair Gordon Lethbridge-Stewart of UNIT from DOCTOR WHO is an
Immortal. In the twenty-fourth century he is a Starfleet admiral. Either he
attained the rank without ever having served off Earth, or Immortals have
learned since Flint's time how not to lose their immortality when leaving
Earth, or he served off Earth in full comprehension of the consequence; or
possibly (as suggested to me by HIGHLANDER fan
Rob Morris) Flint pulled a
fast one on McCoy in the first place. I don't know.
The adversaries in this story are self-appointed successors to the Four
Horsemen as portrayed on HIGHLANDER: THE SERIES.
Picard and the Doctor are not Immortals. They were just helping out
(and, as suggested by the trailer I've seen for HIGHLANDER: ENDGAME, by the
twenty-fourth century there will be precedent that there are allowances to
the rule that all Immortal duels are one-on-one). As you can see if you look,
they didn't share in the Quickening.
I know why it is that Flint claimed in Requiem for Methuselah to have
been Merlin and yet the Doctor was told in Battlefield that a future
incarnation of him will be Merlin, but I have yet to write it into anything
so you'll just have to wait.
(If there's anything in HIGHLANDER about the true identity of Merlin to
further confuse matters, I'm ignorant of it and would welcome enlightenment.)