Vongerella

In the aftermath of the Yuuzhan Vong War, a female Force-sensitive Yuuzhan Vong was seduced and trained in the dark side of the Force.

Biography
Most of the activities of this Dark Jedi were unknown, but it was known that she corrupted the Jedi Knight Daye Azur-Jamin. Hiding in the Cloak of the Sith region, he then managed to capture Kyle Katarn who was investigating rumors of a reemergence of the Sith.

Kyle was rescued by a team put together by Jan Ors, Mara Jade Skywalker and Jaden Korr. The cyborg Daye was subsequently turned back to the light. He then revealed not only the presence of this Force-sensitive Yuuzhan Vong, but also that she had a master.

Behind the scenes
This Dark Jedi was mentioned in an adventure seed in The Dark Forces Saga. She has no official name but was dubbed Vongerella on the Jedi Council Forums. Abel G. Peña later used the name informally.

While her master was never specifically identified, most fans assumed that it was Lumiya; however, after the start of Legacy, some fans have theorized that it was Darth Krayt. The fact that Vongerella is slated to be in the Vader's Legacy article, which also will discuss Lumiya, also possibly hints towards Lumiya.

According to Peña, the Vader's Legacy article includes a backstory and name for her.