The Voraxx were a trade consortium, known for their skills as buyers and sellers, in particular to engage in slave trade. The Second Doctor considered them to be very "bad" and "nasty".
Known members of the consortium were humanoid crocodiles, dressed in suits. Their technology included trans-mat devices and spaceships.
The Second Doctor, in an attempt to take down the slave market, placed a homing device on Jamie McCrimmon, and followed some Voraxx into Stellar Imports & Exports to gain their attention. A member told the Doctor that Jamie, coming from the past was worth a mint. When he said Jamie wasn't for sale, the Voraxx members followed them. The Voraxx kidnapped Jamie, and took him aboard a slaver ship in orbit. Following Jamie's signal, the Doctor and Zoe Heriot found the trans-mat that led to the ship and found Jamie. They then awoke some Ice Warriors, who started an uprising. The slaves took over the ship, forcing the slavers to leave. (COMIC: Prisoners of Time)