Cleaners and cooks. Doctors and nurses. Even drivers and elevator operators. All the support staff for the cardinals who will elect the successor to Pope Francis must take an oath of secrecy.

Workers and clerics assisting the dozens of Catholic cardinals set to gather Wednesday to begin voting on the next pope had to swear to never reveal anything about the proceedings or else risk the Church’s gravest punishment: religious banishment. The employees took their oaths in the Papal Chapel.

Dozens of Vatican staff members, including security, housekeeping and maintenance workers, are sworn to secrecy regarding anything they witness during the upcoming papal conclave.

Beyond simply picking who the next pope will be, players and gamblers also can guess how many tries it will take the cardinals to choose the leader, which day of the week he’ll be elected, what new name he will decide on, or where his priorities will land on the progressive-conservative scale.

All of the 133 cardinals expected to take part in the secret conclave to elect a new pope have arrived in Rome, the Vatican said on Monday, with the race to succeed Pope Francis seen as wide open.

Many of the cardinals said that the jury is still out as they are still getting to know one another and where each of them stands during the general congregations where they gather to discuss issues ahead of the conclave.

A papal conclave is set to begin in Vatican City starting May 7, during which cardinals from around the world will elect the next leader of the Roman Catholic church. The tradition occurs any time a pope dies or resigns from the office. Here's what to know ahead of this week's conclave.