Thalia May was a Human female Sith student who attended the Sith Academy on Korriban during the Jedi Civil War.
Thalia May and a group of fellow students from the Sith Academy on Korriban refused to execute a group of civilians from the nearby Dreshdae colony on the orders of Headmaster Uthar Wynn. In response, Uthar ordered the students executed as punishment. Before the sentence could be carried out, May and her companions escaped into the nearby shyrack cave. No one from the Academy was willing to brave the dangers of the caves to find them and carry out Master Uthar's order.
This was the case until Revan arrived on Korriban during his quest to locate the Star Forge. Revan killed the resident terentatek in the cave, allowing May and her friends to escape off-planet via a passage to the surface. Before leaving, May expressed her thanks to Revan and her wishes to seek guidance in the light side.
If the player character is a dark-sider, then they can go into the caves and agree to "do this the hard way" when May declares she'd rather die than go back to the Academy. Unwilling to go without a fight, May and her companions open fire and are mercilessly cut down.