Huon particles were a type of particle that existed during the Dark Times of the universe.

Huon particles were originally destroyed by the Time Lords near the end of the war with the Racnoss due to their deadly nature. The Racnoss used them in their technology, to power their spacecraft and wake the hibernating young Racnoss at the core of the Earth. The only known remaining concentrations of Huon particles were small amounts in the heart of the Doctor's TARDIS. (TV: The Runaway Bride) They were recreated in liquid form using equipment at the Torchwood Institute by Torchwood One. (AUDIO: In the Shadows)

Huon particles could be created by using a hydrogen base to create them in liquid form. These inert liquid Huon particles needed to be activated in a living being, such as a human. The Huon particles could be mixed with other liquids and drunk, slowly poisoning the victim. This process could take as long as six months or as little as a few minutes, depending on the amount consumed. Once activated, the Huon particles would start to glow and become magnetised, attracting and being attracted to other Huon particles. If enough were absorbed, it could even pull other Huon particles from different time zones (such as the TARDIS ). (TV: The Runaway Bride)

Jack Harkness speculated that Racnoss huon particles may have resulted in the Blessing, but was forced to admit he had no idea. (TV: The Blood Line)