Unidentified planet (Nagi Tsukumo)

A terrestrial planet had a population that the human Jedi Knight Nagi Tsukumo provided aid to at a point between 18 BBY and 3 BBY, during the Great Jedi Purge. However, the planet's people took advantage of a bounty for Tsukumo's capture and betrayed and poisoned him. Although Tsukumo escaped the planet, he did not receive proper treatment for the posion, which left him in a permanently weakened state that required him to wear a mask with a breathing support unit and ultimately killed him.

Text and facts from the “Unidentified planet (Nagi Tsukumo)” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.