An Imprimatur, (PROSE: The Two Doctors, Interference - Book One, et al.) also called an Imprimiture or bio-imprimatur, (PROSE: The Book of the War) was a type of Gallifreyan technology used by Time Lords to design or modify biodata.
The Rassilon Imprimatur was a code designed by Rassilon and added to Time Lord biodata. (TV: The Two Doctors, et al.) This bio-imprimatur protected its recipients from deep time phenomena (PROSE: The Book of the War) and allowed them to put themselves in different time states by focusing on equations. (PROSEl: Interference - Book One) This enabled Time Lords to travel in the Time Vortex (TV: The Two Doctors, PROSE: Divided Loyalties) and transmigrate. (PROSE: Interference - Book One)
The Catherion Imprimiture was an experiment, initiated by the Imperator, that involved modifying casts into new weapons called babels. Its name derived from the extinct House Catherion, whose chapterhouse was used to house the project. After fifty years, the experiment was ended when one babel escaped and massacred the inhabitants of the house. (PROSE: The Book of the War)
The Imperiatrix Imprimatur was a biodata imprint of Imperiatrix Pandora that infected Romana and, later, Braxiatel, who each resisted its influence with limited effectiveness. (AUDIO: Lies, The Curse of Fenman, et al.) Pandora eventually used the Imprimatur to build herself a new body. (AUDIO: Imperiatrix)