Tethir Xiloscient was born 29 Ches, the Year of the Worm, within Suldanessellar, high among the trees of the Wealdath, the son of Quarion Xiloscient and Sariel Amastacia. While he was but a toddler the very gods walked the earth during what would later be known as The Time of Troubles. At twelve he and Sariel fled to Myth Rynn as the motions set forth by the outcast
Joneleth brought war to Suldanessellar. During the next 7 decades Tethir’s years were equally divided living amongst the Ar'Tel'Quessir of his father's tribe and the Sy'Tel'Quessir of his mother's, but never did he visit the two together. He was raised by his father, who unbeknownst to him was part of a cell of the Eldruth Veluuthra, to despise all N'Tel'Quess especially humans.
He and the other children of his tribe would frequently join the adult hunting parties as they stalked humans that dared to enter the Wealdath. Occasionally, as these children edged ever closer to declaring themselves adults, they would hunt humans without the guidance of adults. He learned well to be cruel and swift in his punishment for perceived slights against the lands of Tel’Quessir.
Although he respected Quarion and had a great desire to make his father proud, he found he enjoyed his time with Sariel, alone in the forest, much more. This had little to do with the fact that he bore a stronger resemblance to his mother's kin than his father's. His mother, a great druid, instilled in him a love of the forest and a respect for the balance of nature. She was well aware of the monster Quarion was raising her son to be. It was her desire to temper Tethir’s genocidal tendencies and she vowed to herself that she would be the counter balance to his father’s teachings.
Near Tethir's 80th nameday Sariel began tutoring a young human boy, named Malgrym, in the ways of the elves. Tethir was appalled that his mother would allow a human to enter the Wealdath, but in time he came to not only accept the boy, but to begrudgingly befriend him. Sariel made Tethir promise never to mention Malgrym to Quarion.
Over the next two decades Tethir wintered with his father, learning the ways of warfare while hunting humans, and spent the fairer months in the forest with his mother and Malgrym. Though Tethir was still a youth and yet played with the Sun Elf children of his father's Elmanesse tribe, Malgrym quickly became a man. As they sparred and trained together, Tethir couldn't help but notice how much more driven Malgrym had been and how quickly his skills had progressed. Malgrym had grown up while Tethir barely aged. The lines had blurred as to which was the more skilled ranger.
In Alturiak, The Year of the Plotting Priests, word reached Quarion that Sariel had been harboring a human within the Wealdath. He ordered Tethir to return to her immediately and slay Malgrym. When Tethir arrived he found his mother with Malgrym. As he prepared to loose the arrow that would end Malgrym’s life, she stepped between the two and revealed to Tethir that she was carrying Malgrym's child. Tethir demanded Malgrym leave the Wealdath and never return on pain of death.
For the next year Sariel taught Tethir to move about the forest to avoid being located by the Eldreth Veluuthra. The half-human infant proved to be too much for Sariel's small elven body and she died giving birth. She left Tethir a journal detailing that she knew she would not survive which also contained instructions for him to assist with raising his brother, Yuri, named for Malgrym's father.
It was on this day, 4 Ches, The Year of the Forged Sigil, that Tethir Xiloscient shrugged off the mantle of childhood and declared himself an adult. He adopted the name Thyrricean Amastacia and spent the next two decades moving from place to place to ensure the Eldreth Veluuthra never found his brother.