The Senites controlled access to their planet using a shield that allowed people to come down to the planet, but not return to space once under the shield. Those who landed ships on the planet had their space vessel immediately confiscated and deposited at the Graveyard of Lost Ships. The Senites were extremely hostile towards most outsiders, usually ignoring communications from those off the planet and only talking briefly when they did choose to respond.
In order to provide for the inhabitants of the planet, the Senites worked in a variety of roles. This included everything from working as cooks and waiters to street sweepers to prostitutes in areas with few women.
The Senites did not have one uniform physical appearance because of their method of reproduction. Rather than a biological process, the Senites reproduced by capturing inhabitants of the town of Dohama and transforming them into Senites via the Reborning ceremony. Inhabitants of the planet were not told of this process and the Senites carried it out using a process that involved drugging the residents of the town before transforming them.
In 2268, Captain James Kirk, Spock, and Leonard McCoy were trapped on Sanctuary and the Senites refused to let them escape. This led the trio of Starfleet officers to attempt various escapes from the planet, interfering with the Senite way of life and actually disrupting a Reborning ceremony. Once the three successfully escaped the planet, the Senite Zicree said the Senites might choose to change their way of life in response to what had happened. (TOS novel: Sanctuary)