Sethra the Younger is a Dragonlord (her lineage, and indeed, her original name, has not been disclosed), who apprenticed herself to Sethra Lavode, and took the name "Sethra" in order to honor her mentor.
In return for this service, she was granted the post of Warlord.
Sethra the Younger is the only apprentice that Sethra Lavode has had so far who did not try to kill her. Instead, Sethra the Younger manipulated the Dragon succession so that under the next Emperor, she would either be Warlord or the Warlord would be someone who didn't mind if she invaded the East.
Her manipulations resulted in the deaths of K'laiyer e'Lanya, the rightful Heir of the e'Lanya line, and his spouse Miera, resulting in Adron e'Kieron becoming Heir (again), which was rather more unfortunate than it should have been, as no one could have expected Adron to destroy Dragaera City and cause the Interregnum.
Sethra Lavode declared she would rather that Sethra the Younger have made an attempt on her life, and punished her former apprentice by sending her to another dimension to write "I will not interfere with the Dragon Council" 83,521 (174) times. The Empress punished Sethra the Younger by declaring that she could never hold any Imperial post. This disgrace led to her termination from the post of Court Wizard which she occupied at the time these machinations became known.
Sethra the Younger claimed the Morganti greatsword that was hiding Pathfinder at the Battle of Baritt's Tomb, but later traded it to Aliera e'Kieron for Kieron's Greatsword, which she intends to use to conquer the East.