A wetworks facility, technically known as an aqueous data storage system, was a machine used to store information. Most wetworks facilities only had a capacity for a few gigabytes. The Time Lords built the Matrix after a failed attempt to create a wetworks facility.
In the Library on Kar-Charrat, Chief Librarian Elgin used the native lifeforms to construct a wetworks facility capable of housing the entire knowledge of the universe. He was unaware that this came at the expense of sentient beings.
The Daleks seized control of the Library and made two attempts to download the information in the wetworks facility into a test subject, thus creating the ultimate Dalek which would aid them in their plans for conquest. The first went insane and rampaged through the Library, while the second gained a respect for non-Dalek life and refused to obey orders to kill and destroy. The Seventh Doctor had Ace plant explosives which killed the Daleks and destroyed the wetworks facility, freeing the Kar-Charratans. (AUDIO: The Genocide Machine)