The Bruydac were a species from the planet of the same name.
The Bruydac were humanoid, with a powerful build but thin arms. They were over seven feet tall and capable of picking up a human. They had two eyes, a wide mouth and a bony crest on their head. (PROSE: Another Life)
Bruydac technology was partially organic in nature, as seen in their ships. The floors were spongy, the lighting was a pale green, fronds and tendrils grew from the ceiling and communication was by glowing sigils on the walls.
The Bruydac had a history of invading other planets, using devices implanted in the brainstems of the natives to possess their bodies and infiltrate the planet's society. The implant was placed in the upper spine, allowing an individual Bruydac to possess the host. Though some of the original memories and personality remained, the Bruydac had complete control. The Bruydac could only control one host at a time, but could jump from host to host, provided the hosts were alive and conscious. The implant also created a need for spinal fluid, which the hosts gained by biting open the skulls of other people. The host could produce starfish-like creatures in their stomach, which could be vomited up in defence. These "starfish" would produce an acid that could dissolve organic material and, if allowed to grow, the starfish could overpower a human. (PROSE: Another Life)
Circa 2007, a Bruydac ship was caught in the Cardiff rift and stuck under Cardiff Bay. All but one of the crew were killed, and the survivor was badly wounded. At the same time, Guy Wildman, Anthony Bee and Sandra Applegate were going SCUBA diving in Cardiff Bay. When they found and entered the ship, the Bruydac warrior was able to overpower them. He implanted them each with implants and then let them out to find something to repair his ship. Anthony was killed by his soldiers when he tried to steal supplies for the Bruydac. Though Guy was able to use his connections with Blaidd Drwg to steal 6 uranium cores, he too was killed by Torchwood Three when he fed on too many people. When Sandra tried to get back the uranium cores she was badly wounded.
Sandra was able to lie and convince Owen Harper and Megan Tegg to come to the Bruydac ship. Once there, the Bruydac implanted them both and sent out Megan to finally get the uranium cores (and kept Owen as a spare host). Jack Harkness was able to kill her before she got the cores back and had Owen hunted down. Jack killed the Bruydac's body, implanted himself and had Owen tranquillised, leaving only himself as a potential host. He was then drowned with Bruydac in his body, killing it permanently. (PROSE: Another Life)