Disclaimer: I do not own Lord of the Rings material or benefit financially in any way.
Authors Note: A bit of backstory on how the elves ended up in Fangorn.
Prologue
There was one that was never accounted for, one that seemed to disappear into the whispers and lore of Middle Earth. Maglor of the House of Fëanor was neither dead nor alive, his whereabouts and that of his kin are a mystery that few ponder. There were rumors and stories of his demise as well as rumors of his curse to forever wander the seashore in search of his Silmaril and never return to Valinor. It was a tale that had all but faded into memory, forgotten as time pressed on.
There are only handfuls that remember the Mighty Singer and even fewer that remember his children. There were no tales sung of his sons and daughters, they were lost to history as were their friends and followers that disappeared in the Second Age. A whole community gone and not missed by the other elves of Middle Earth.
The decision was made by Maglor's son Marcous to leave after his wife's death in the Last Alliance battle. He pleaded with his mother to come with them to Fangorn but she refused, she would not leave her home near the sea. She had hoped that someday Maglor would find his way back to her. Marcous knew his father's mind was gone and that he would never return. His mother would fade as she waited for a man that died long ago to return. With a heavy heart full of grief from the loss of his wife and now his mother, Marcous led several hundred elves by the cover of night into the one place few dared to go… Fangorn Forest. It was protected by an ancient magic that elves and men alike feared. Marcous knew this was a false fear. He knew the truth about Fangorn and the magic that protected it. His father had shared it with him before his mind had failed.
Marcous led his followers deep into Fangorn to its heart where the Onodrim lived. Marcous worked out an agreement with Treebeard their leader to protect Fangorn from the orcs and man if they could find sanctuary within its borders. The Onodrim agreed and helped Marcous and his followers build a city near the river called Wellinghall. For nearly a thousand years they lived in peace and harmony within the forest. Marcous established the Watchers, highly skilled elven rangers who watched the borders of Fangorn and protected it from harm. Never had Fangorn and the Onodrim been as protected as they are under the watchful eyes of Marcous' rangers. Both the elves and the Onodrim benefited greatly from the arrangement.
Even Fangorn and its elves are not safe from the shadow that approaches from the east. Dark times have a way of drawing out that which is hidden and binding together the most unlikely of allies. Fangorn and Rohan's survival may depend on one Watcher and one Marshal of the Mark to bring them together to battle the evils of Sauron.