Atris is a character from Star Wars: Knights of the Old Republic II: The Sith Lords, in which she serves as a major antagonist. She is a fallen Jedi Master and one of those Jedi who banished the Exile and later one of the Jedi Masters that had survived and escaped the First and Great Jedi Purge during the Dark Wars at the hands of the Sith Triumvirate, only to then eventually succumb to the Dark Side.
After the end of the Great Sith War waged by the ancient Sith Lord Exar Kun and his Sith apprentice Ulic Qel-Droma, the Jedi historian Atris attempted to revise the broken system of Jedi apprenticeship. She argued that there was little wonder why Kun and Qel-Droma fell to the Dark Side, when the Jedi had liberal instruction practices in place, such as dozens of Padawans training under a single Master, the radical bonds of reciprocal apprenticeship, and Jedi beginning their training in their teens and later. She invoked thousand-year-old recommendations first suggested by the Jedi Master Simikarty, lobbying for the restriction of Padawans that a Master could have at one time, and also limiting the age of Jedi candidates.
Atris also advocated prohibiting romantic involvement for Jedi, citing that the First Great Schism had been started by two lovers. She even endorsed adoption of a more austere interpretation of the Jedi Code which was favored by the Draethos Jedi Master Odan Urr, in memory of his death at the hands of Exar Kun at the Jedi Academy on Ossus. Her arguments found powerful purchase amongst the Jedi, and she was appointed to High Jedi Council on Coruscant.
During the Mandalorian Wars, she was deeply committed to the Order and was a fierce adherent of the Jedi Code. But Atris' faith in the righteousness of the Jedi wavered when her personal hero, Meetra Surik, turned her back on the Council to join rogue Knights Revan and Malak and their faction of Jedi during the Mandalorian Wars. Atris chose not to go to war, but this decision left her bitter and conflicted.
The Jedi Purge
When Surik returned to face the Council's judgment after the devastating events of the Battle of Malachor V, Atris was the first to condemn her, suggesting that she had fallen to the dark side just as Revan had. Over time, Atris grew to hate Surik for complicating her black-and-white view of the Sith, the Jedi and the Force. During the Dark Wars and the first and great Jedi Purge, Atris called a secret Jedi gathering on the Miraluka world of Katarr in an attempt to find the threat that was stalking the Jedi. She then leaked knowledge of the conclave's existence in the hopes of drawing out the Dark Lord. She succeeded, but with dire consequences; the master, Darth Nihilus destroyed the surface of the planet, wiping out all life on Katarr, including the Jedi gathered there.
Atris remained in seclusion, surrounding herself with Echani Handmaidens who could not feel the Force. She planned to rebuild the Jedi Order, and established an academy in the old irrigation system on Telos IV. However, she was heavily influenced by the many Sith holocrons she had collected in her efforts to find and understand the Sith. The holocrons fed her bitterness and slowly corrupted her.
Later, she was confronted by Kreia, who had now taken up the identity of Darth Traya again, and Traya stripped away her illusion and brought her truth so that her teachings could be ended before they began, finishing her corruption and ultimately turning her to the Dark Side. After Traya had left, Meetra Surik returned and fought Atris and defeated her in a lightsaber duel. After a long talk, Meetra redeemed Atris and Atris let go of her anger and hate and turned back to the light. It is unknown what happened to Atris afterward but it has been presumed that she rotted and passed away remaining on the wastelands of Telos IV or she was killed by the Sith holocrons.
If the player's character in KOTOR II is dark sided however then the character can choose to kill Atris or leave her at the mercy of the Sith holocrons.