- "The High court of Yevon is now in session."
- —Maester Kelk Ronso at the opening of Yuna's Trial
Kelk Ronso (ケルク＝ロンゾ, Keruku-Ronzo?) is the leader of the Ronso, and a Maester of Yevon in Final Fantasy X. Kelk speaks with much eloquence for a Ronso; since he is a Maester of Yevon, he most likely grew up in Bevelle in order to learn his duties as a Maester. This could explain his human-like speech and sophisticated mannerism, quite unlike the broken English spoken by most other Ronso.
Kelk does not appear until the events at Bevelle. He is in charge of administering Spira's judicial system and puts summoner Yuna and her guardians on trial for the murder of Maester Seymour. He is the only one of the Maesters unaware that Seymour had killed his father, Jyscal, and it troubles him greatly once he discovers this fact. Following Yuna's sentence, Kelk has had enough with Yevon's hidden secrets and betrayals, and returns to Mt. Gagazet hoping to find honesty and order in his mountain home.
When Yuna and her guardians reach the Mountain Gate, Kelk denies them passage up the sacred mountain because of their unusual interactions with the Al Bhed and Yevon. Upon realizing Yuna is still willing to sacrifice herself for the good of Spira, even after turning her back on Yevon, he praised her resolve, and lets them pass.
Shortly after, Seymour comes up the mountain, intent on continuing his mission to become Sin. Kelk had promised Yuna and her guardians he and the Ronso would bar the path of any intruders wishing them harm. Seymour was thus prevented passage, which angered him, and caused him to slay every Ronso in his path, including Kelk.
- Kelk is the only Maester who is neither seen nor mentioned at all in Final Fantasy X-2. Seymour had previously died and been Sent to the Farplane, but his influence upon the Guado left grave repercussions in Final Fantasy X-2. Wen Kinoc, Jyscal, and Yo Mika are seen and fought in Via Infinito as bosses Aranea, Black Elemental, and Concherer, respectively. Kelk's total absence from Final Fantasy X-2 likely suggests he had simply accepted his death at Seymour's hand.