#1 is not OLD FOREST but a much earlier and less famous "land of shadows". You may have forgotten about it. A lot of people did, unfortunately for them. <--hint.
#2 is not UNGOLIANT. You were closer before. It is a thing, rather than a "Person, Beast or Monster".
#4 is ERED GORGOROTH. "Legendary one walked valley, bewildered" is the cryptic part. I'll explain if you like.
#5 is MELKOR (backwards). "Echo" does refer to Lammoth, but is more a hint to how the answer relates to the theme.
#6 is the right approach, but the answer is an *even prettier* pass.
1. Incarnation has a solitary element in this land of shadows.
2. Unsettled surfeit for the insatiable.
3. As he reflected, he lived in high places, in the company of a noblewoman.
ERED GORGOROTH Legendary one walked valley, bewildered, in dreadful mountains.
ROKLEM (Melkor) A mighty avant garde soloist, in retrograde. Or is that an echo?
6. Twice-twisted suffering? We have come to a pretty pass.
7. A venomous insect, yes- but me, a mixed-up globule? Take it back!
PHIAL OF GALADRIEL: Star-power? She bottled it!