780 years before the events of Radiant Dawn, Ashera, the goddess of order, decides to destroy her counterpart Yune, for she thinks Yune disrupts her perfection and the peace in the world. However Lehran, her closest consultant, pledges her not do do so, but to seal Yune into a bronze medaillon instead. Ashera finally agrees to his counsel and promises, if there will be no war on Tellius for 1000 years, she will allow Yune to be freed out of her prison and to reunite with her. If the Beorc and Laguz are not able to keep the peace for this time, Ashera will destroy the existing world immediately. However, if she is waked by the Galdr of Release, she promised to first have counsel with Yune before acting.To alienate the Beorc and Laguz from commiting war, Yune, imprisoned in the medaillon, is later said to be a dark god, who will destroy the world if it wakes.
Several years before Path of Radiance takes place, the Mad King Ashnard gets hold of Lehran's Medallion and plans to pitch Tellius into war by freeing this dark god. To do so, he kidnappes Lillia, a heron princess from the clan of the Serenes, to sing the Galdr of Release. He keeps her locked in a windowless room in Palmeni Temple, where Elena sees to her well-beeing. However, Lillia is not able to release Yune from the medallion, as her powers fade from exhaustion. Lillia then passes the words and the melody of the Galdr and the Medallion to Elena and eventually dies in the Temple due to her bad condition. Elena then leaves Palmeni Temple, with the actual plan to bring the Medallion safely back to Serenes, but she and her husband Greil had to flee from he Daein armee for several years, and finally seeked refuge in Gallia.
Greil once undeliberately touched it and it drove him to complete madness, until he ended up killing Elena. When Ike was little he was scolded harshly by his father for attempting to touch the medallion. If one touches it, the Medallion magnifies the worst aspects of a person thousandfold. The proportion of order to chaos also affects the effects of the Medallion on the person who touches it. Only persons who had order and chaos in complete balance were able to touch it uneffected. Mist and her mother Elena were the only beorc known to carry it safely, while the heron royals also can do so. After Elena died, Mist inherited the Lehran's Medallion from her, though believing it to be only an ordinary medallion. However, to the end in Path of Radiance, Mist learns about its true qualities.
In Hard and Maniac modes in Path of Radiance, Ashnard touched Lehran's Medallion after Ike defeated him the first time but somehow retained some portion of his sanity. It is possible, as someone already strongly attuned to the forces of chaos as a result of his insatiable bloodlust and insanity, that the Medallion simply did not have that great an impact on him. Either way, it is only at this point that the player can call up the laguz royal of their choice.
In Radiant Dawn, during the final of part 3, the chaotic energy of the medallion increases due to the fighting, until eventually Mist, Reyson, Rafiel and Leanne collapse. Mist advises to wake the dark god with the Galdr of Release instead of doing nothing, so Micaiah, at this moment already posessed by Yune, sings the Galdr and Yune is freed. Although Ashera promised first to discuss about the punishment for the Beorc and Laguz with Yune, she immediately judges them by turning almost every single inhabitant of Tellius into stone. Yune and the remainig, spared by the judgement (which are actually all playable characters in the game) decide to face Ashera in the Tower of Guidance.