Aridius was a planet originally covered by oceans. Due to a stellar incident, its orbit around its suns turned the planet into a desert over a thousand years. The only remaining species were the amphibious Aridians and the octopus-like Mire Beasts.
The First Doctor visited Aridius, but was tracked by the Daleks. (DW: The Chase)
Behind the scenes
According to non-narrative information in DWBIT 41, the Daleks later returned to Aridius, still remembering their encounter with the Doctor there. They wanted revenge on the Aridians and wiped them all out along with the Mire Beasts.