The thing that wouldd seem to me to be the definition of a troll is
that they are descended from Kyger Litor and, I would think in the
case of the Kitori, choose to acknowledge that descent or not. Seems
to me that ancestry is more a function of conscious choice in
Glorantha than it is in our world (although I would suggest that it is
more important in our world than we sometimes think - deciding that I
am English, for exampe, is not really a genetic thing more a
cultural/conscious choice)
Clearly there are darkness beings, men and gods who are not descended
from Kyger Litor yet are darkness men.
I like Peter's suggestion for the different sources of trolls. I would
probably expand his point to include all humans - they come from
different places/myths, but are now intermingled, in varying degrees.
Keith