Appearance
She fights with the Sword of the Sun, which glows in her hands.
Activities
She is not explicitly mentioned or shown as being present when Matrim Cauthon blows the Horn of Valere at Falme. Mat recalls the name and her presence there only later when he recognizes Birgitte Silverbow. When Egwene al'Vere is captured by the White Tower, Nicola Treehill, and Areina Nermasiv compare Egwene to Amaresu and Birgitte.
When Olver blows the Horn of Valere, Amaresu is called forth with the other heroes. She chastises Mat Cauthon for having constant doubts about Rand's sanity, and that he owed Lews Therin his life twice over.
Parallels
Amaresu is a parallel of Amaterasu↗, who is the Japanese Sun goddess and an important Shinto↗ deity. She is the ruler of Takamagahara↗, the abode of the heavenly gods, and is one of the three most important children of the creator god Izanagi↗. She is the mythological ancestor of the Imperial House of Japan, with the legendary first emperor Jimmu↗ supposedly being the great-great-great-grandson of Amaterasu. The Ise Grand Shrine↗ where Amaterasu is worshipped is one of Shinto's holiest sites, and the priest or priestess of the site must come from the imperial house of Japan.
Her name is also reminiscent of the literary term Mary Sue↗, a character archetype, usually female, who is "inexplicably competent across all domains, gifted with unique talents or powers, liked or respected by most other characters, unrealistically free of weaknesses, extremely attractive, innately virtuous, and/or generally lacking meaningful character flaws." Someone who is ta'veren and/or destined by the Pattern to be victorious might be called "A Mary Sue". Egwene, compared to Amaresu by Nicola Treehill, is often (possibly unfairly) accused of being a Mary Sue in the Wheel of Time fandom.