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 1,000 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)
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. (DWBIT: #41 - Dalek Wars)