"organized a group with a shared purpose" here, to kill Paul.
# called a curse down upon themselves with an oath
The noun "curse" can be translated as a verb. It can also be made explicit what would cause them to be cursed. AT: "asked God to curse them if they did not do what they promised" (See: [[rc://en/ta/man/translate/figs-abstractnouns]] and [[rc://en/ta/man/translate/figs-explicit]])