Kiaphet Amman'sor was a representative of the Xindi-Aquatics on the Xindi Council in the 2150s. She was a member of the wealthy and powerful Ibix Dynasty, and her opinions carried great weight with the rest of the Council. She was often the peacemaker on the Council, attempting to calm the dissension that often arose. She was very concerned that in-fighting would tear the Council apart.
Amman'sor was at first against building the Xindi weapon to destroy Earth. It was not until the Guardians presented a visual recording of Humans destroying the new Xindi homeworld that Amman'sor was finally swayed. (ENT: "The Council")
Amman'sor rejected Dolim's plan to develop a bio-weapon to destroy the Humans, considering it too dangerous. However, Amman'sor stated that if the weapon being developed by Degra did not work out, she would be willing to consider alternatives. Once Rajiin acquired the necessary information to develop a bio-weapon, Amman'sor voted that they develop both weapons simultaneously. (ENT: "Rajiin")
When Captain Jonathan Archer came before the Council in February of 2154 to present his case, Amman'sor was at first unswayed by his evidence. However, once Archer showed the Council a biometric hologram, Amman'sor agreed to delay the launch of the weapon. (ENT: "The Council")
When the Reptilians and Insectoids stole the weapon, Archer confronted Kiaphet and the other Aquatic councilor. Three hours later, they agreed to help intercept the weapon in exchange that Archer's ship disable the spheres. (ENT: "Countdown")