The Vaal, often referred to as the "red ones," are the oldest known culture in Wraeclast save for the Proto-Vaal. They existed in central Wraeclast and on the island of Oriath. Two of their cities were Azala Vaal and Lira Vaal, and they also had a temple in the jungle named Atzoatl. They worshipped multiple gods, and the followers of Ralakesh enslaved many primitive Azmerians long before the Vaal established peaceful contact with them. They also seem to have had contact with the Templars, as the descry symbol used by the Templars can be found on some of their artefacts, such as Zeel's Amplifier and Vaal totems.
The Vaal were strong advocates of science and the use of Virtue Gems. Their technology was more advanced than that of any other known civilization, including those that came much later. Vaal ruins are populated in part by creatures referred to as "constructs," said by Alva Valai to have been created by combining metal and insects. The Vaal conducted research into such areas as explosives, "electrical lifebloods," bioengineering, and weather manipulation, and they studied other realms, including breaches and maps. They also experimented extensively with human sacrifice and torture--which may have stemmed from the myth that they were created from the flesh of the gods and that it was their duty to return this flesh to them--as well as the Beast's power of corruption.
All of what is known about the Vaal is contained in the corresponding section above. The Vaal were supposedly wiped out in the Fall except for a few thousand refugees. However, there are a couple of hints that indicate this may not be completely true.