The Lizard Keepers were slaves of the Dathomiri witch Zalem. They were assigned to cut off the paws of the native lizards, the Kwi, which were the key to the Infinity Gate. Not every maleling slave became a Lizard Keeper, because that job was a very dangerous one. You only became a Lizard Keeper if you were promoted by Zalem herself.
In 31 BBY, the Jedi Quinlan Vos and the Givin Yag Shushin were promoted to Lizard Keepers when Quinlan slew a giant Whuffa which was attacking the excavation site.