Unknown number of research facilities.
Abathur discovered a special type of scantipede being held at one of the research facilities. This scantipede could implant its victims with parasites that hatched upon their hosts' deaths. Kerrigan sent a group of roaches into the facility to free the scantipede, kill the protoss guards, then kill the scantipede and collect its essence. Abathur then mutated the roaches into the corpser strain, which could implant their enemies with parasites. Upon the host's death, the parasites would emerge as roachlings. These new corpser roaches wiped out all the protoss within the facility.