Brindigulum

A Brindigulum was "a conference or talk between four or more Daleks". None could be held without the Emperor Dalek's consent. (PROSE: The Dalek Dictionary)

One Brindigulum of Daleks on the planet Valkenine featured a number of Daleks from three different castes: transport officials, miners and metalworkers. This Brindigulum was interrupted by rebelling prisoners who took five of each caste as hostages, but one of the transport officials managed to confuse them through "sleight of mind" and mathematical misdirection into thinking one of the hostages had escaped to bring reinforcements; with the slaves now confused and divided among themselves, the Daleks were able to overpower and wipe them out. (PROSE: Hostage!)