The Third Age, Year 916, marks the birth of Cassthiel Isthilgalad, daughter of Elendor and Cara-Marien, in Mirkwood. Though their forest-home has long fallen to the shadow, the Silvan elves believe they will one day restore Greenwood the Great, which is especially desired by Cassthiel, for she loves all woodlands and seeks to protect them until her time in Middle-earth comes to pass.

In her early years, which for elves are marked by their first centuries of immortality, Cassthiel honed her skills as a huntress. Under the command of King Thranduil, the elf-maid fought besides her kin against the spiders of Mirkwood. A millennium soon passed, and she became restless with a curiosity of the world beyond the dark woods.

With great haste, Cassthiel departed from her forest-home, biding farewell to her friends and family, to wander through the lands of Middle-earth. 

Cassthiel Isthilgalad now dwells in the valley of the river Withywindle. There she cares for the good animals of the Old Forest and keeps the ancient flowers of the entwives company. Her heart, after the doom of the ring, no longer desires adventures or battles. Instead, she seeks to protect the nature of the world and to spend her days full of laughter. From time to time, she wanders through Middle-earth to enjoy festivals and partake in merry-making. The Free Peoples who have seen her have given the elf-maid many names. To the hobbits of the Shire, she is known as Dahlia. The men of Bree have named her Mona, and the dwarves of the mountains know her as Norvi. She will gladly guide strangers of the Old Forest, who need only ask for navigation. 

Though the peaceful days of Middle-earth will flourish as the Fourth Age passes, Cassthiel knows her time in the world will come to an end. The woodland elf-maid will one day leave the Old Forest and make one last journey to her true home in Mirkwood. There she will gather her old friends and family and sail west, never to return to the mortal lands.