Teersa is a High Matriarch of the Nora tribe. She promoted Aloy to a Seeker so that she could find out what happened on the day of the Proving. A member of the High Matriarchs, she attempts to lead the Nora with compassionate wisdom, and is often at odds with Lansra.
Acting as the primary form of government for the Nora in both political and religious matters, Teersa, Lansra and Jezza attempt to lead their tribe through many situations, from following the customs of the All-Mother to war with the Mad Sun King Jiran.
However, while heading inside All-Mother mountain, they discovered a baby girl lying before the door of the All-Mother. Believing that this child was of importance, Teersa tried to make the other Matriarchs understand, but Lansra did not see eye-to-eye on the matter, believing the baby to be a danger to the Nora, and therefore had the child given to the outcast Rost to look after.
Events of Horizon Zero Dawn
Against the other Matriarch's wishes, Teersa discreetly had Rost bring the baby to the overpass of All-Mother's mountain to make the babies' name be accepted. Rost gave the name Aloy, which Teersa declared to be accepted, but they were soon both confronted by Lansra and Jezza, who did not agree on the naming of the baby. They sent the child away, much to the disagreement of Teersa.
Teersa and Aloy did not meet again until the latter turned 19, and Teersa was overjoyed to see her again. However, she could only provide encouragement on the Proving, and sent Aloy to see a friend of hers. She, along with the rest of the Tribe, was shocked to learn of the massacre of the candidates of the Proving, with Aloy as the sole survivor.
Against the wishes of Lansra, Teersa allowed Aloy to recover in All-Mother's Mountain. When Aloy recovered, Teersa took her to the door to explain the circumstances Aloy's birth. When she stood in front of the door, a female voice and a bright red beam scanned Aloy, but failed to allow her entrance due to corruption. Teersa interpreted this as meaning that Aloy should heal the world of corruption, and named the girl a Seeker to seek out the answer to the problem.
While maintaining order in the Nora tribe, the tribe was attacked by the Shadow Carja and corrupted machines. Fearing total annihilation, Teersa allowed the surviving tribe members into All-Mother's Mountain. She discussed with the matriarchs what to do, when Aloy returned with access to the All-Mother, which both amazed and humbled those present, Teersa among them. Aloy explained that she has a purpose to defeat a Metal Demon, to which Teersa agreed and had the Nora Braves follow to stop this demon. Ultimately, they were victorious in defeating it.