One of the Crystal Warrior exclusive banner characters, Cetia is a Fire ranged damage dealer with a unique main job that more or less works like a modernized Ranger. It comes with a reliable wide-area attack like Barrage (Thermal Exposure+ and a lot of debuffs to weaken enemies hit. Combined with Sniper sub job, she ends up having a lot of utilities in her arsenal to deal with most situations: Removes Barrier/Reraise, DEF/Fire down, disables counter abilities, and lowers healing power.
However, it's worth noting that while she does have AP cost reduction passive and an AP gain increase (if you use Bracchio-Raidus VC), she is still very AP hungry and needs Illusory Bell for consistent damage. She also lacks a guaranteed hit ability as well as somewhat low AGI. Even though she has an AGI+ buff, it might not get used often due to needing bells.