Of Noldor and Sindarin descent, she was born during the early years of the Third Age in Lothlorien, as the second child of her parents. Her brother, sole sibling, was born several years before her.

In Lórien, Idhrelleth first began studying the secrets of nature and the lore of the land. Once she was considered an adult, she also started training as a warrior, learning how to wield sword, staff and spear in battle.

Around the first millenium of the Third Age, her parents felt the calling of the West grow stronger and chose to travel west of the Misty Mountains, to reside in Rivendell for a time. Idhrelleth and her brother joined them around the year 1200. Idhrelleth chose to remain with her parents in Rivendell, while her brother returned to Lorien to serve as a warden of the golden woods.

While in Imladris, Idhrelleth expanded her knowledge over ancient secrets and learnt the art of sword-smithing from the Noldor smiths that resided in the elven refuge.

Around the year 1700, Idhrelleth developed a close friendship with an Elf from Lindon, who resided in Rivendell. For many years their friendship flourished until the threat of Angmar grew very strong in the north. Her friend departed to aid the Dúnedain of Arthedain, amongst which he had many close friends. As a parting gift Idhrelleth crafted what she claims to have been the greatest sword she has managed to create, engraving it with Cirth runes of power and warding. However, her gift was unable to protect her close friend who was slain by an ambush from forces from Angmar, around the year 1970.

Idhrelleth greatly mourned his passing and joined Glorfindel's force that was mustered to aid the Battle of Fornost 5 years later, as a way to avenge her friend. After the defeat of the Witch King's forces, Idhrelleth returned to Imladris for a couple of years before departing for Lothlórien once more.

There, she resided until the year 2748 when she and her brother once again travelled to Rivendell, to stay with their parents for a time. In the year 2759  they accompanied their parents to the Grey Havens, for the calling of the west had grown too strong for them to resist any longer. Her brother returned to Lothlórien.

Since then, Idhrelleth has embraced the path of the wanderer, travelling the wilds of Middle-Earth and periodically visiting elven refuges to rest.