Blood control
From Tardis Wiki, the free Doctor Who reference
Via blood control, an entity could have power over the blood's donor and control their mind and actions. Blood control does have its limitations. Even from space, the Sycorax could control every Human on Earth, in theory, however, as they only had a sample of A+ blood type, they could control only one third of the Human population.
The Doctor said he had not seen blood control used in ages. (DW: The Christmas Invasion)
- The Sycorax probably regarded blood control, like other technologies, as a form of witchcraft or sorcery.
