Ah Legate, fantastic riddle, the clue's in your own name of course! Very sneaky!
My nomination (and in this I am unanimous) is Dol Guldur, aka Amon Lanc, whence comes the Legate
OK so,
Above the trees and above the valleys
ִ̣̣̣̣̣̣̣ ִ ִ around the world I'm looking from high.
I'm a mountain above the trees and valleys of Mirkwood
Before the darkness I found my friends here,
ִ̣̣̣̣̣̣̣ ִ ִ being here before darkness was cast.
Calm touch of sun was still on my face,
ִ̣̣̣̣̣̣̣ ִ ִ clouds of shadow were not upon me.
Before Sauron came it was a habitation of friendly elves
Dangerous time has settled on the world,
ִ̣̣̣̣̣̣̣ ִ ִ doubt and doom coming to Wise men of old.
The time of the Last Alliance
Even though High Man was in my sight
ִ̣̣̣̣̣̣̣ ִ ִ early he died, no one could help.
Far from home he died, I am a witness
ִ̣̣̣̣̣̣̣ ִ ִ fear will fall on all because of this.
Isildur ambushed by the orcs at the Gladden Field
Grave times then came, and to me as well
ִ̣̣̣̣̣̣̣ ִ ִ great deeds were done, but I knew of naught.
Hope and its bringer I have seen from afar,
ִ̣̣̣̣̣̣̣ ִ ִ have been observing the tide that has turned.
I was lost yet though, abandoned by friends,
ִ̣̣̣̣̣̣̣ ִ ִ in creeping darkness I was left alone.
Sauron occupied Dol Guldur around 1000 TA
Kindness don't seek at me - from the dark times,
ִ̣̣̣̣̣̣̣ ִ ִ knowledge of me is knowledge of shadow.
My name was taken away from me long ago,
ִ̣̣̣̣̣̣̣ ִ ִ may someone yet still remember my name?
Now I am story of fear among once-friends,
ִ̣̣̣̣̣̣̣ ִ ִ name of mine recalls only tremor.
remember my name
Dol Guldur - Amon Lanc, we still remember you!
Over my garden I look still in fear,
ִ̣̣̣̣̣̣̣ ִ ִ oh, what if all of it comes into dark?
Prison of stone now stands where I be
ִ̣̣̣̣̣̣̣ ִ ִ past joy forgotten, cold stone is all.
The Necromancer's fortress
Really there's no way to lift curse of mine?
ִ̣̣̣̣̣̣̣ ִ ִ rare hope appears sometime - soon to be gone.
Stars have been hidden, darkness will return,
ִ̣̣̣̣̣̣̣ ִ ִ seven times stronger the darkness will come.
Dol Guldur occupied wth sevenfold stremgth before the War of the Ring
There was the man who came to the wall,
ִ̣̣̣̣̣̣̣ ִ ִ to my gate came once weary wanderer.
Verily, was it just wisdom he sought? Or more? -
ִ̣̣̣̣̣̣̣ ִ ִ victory's key was what I gave to him.
Gandalf's two missions to the mountain
Warder I became to them who my Lord brought,
ִ̣̣̣̣̣̣̣ ִ ִ woe betide those who come to know me!
Years uncounted must have passed by me -
Dol Guldur is Sauron's prison
ִ̣̣̣̣̣̣̣ ִ ִ "Yield!" I hear. "Darkness, leave him at once!"
Zenith of sunlight - can it be true?
ִ̣̣̣̣̣̣̣ ִ ִ zither and horn, I am free again!
But after the victory of Frodo and Sam, Galadriel and co. cross over to Mirkwood, changing it back to Greenwood the Great and perhaps Dol Guldur to Amon Lanc again