Morraxian

The Morraxians were a humanoid race native to Morrax. They had large, dark eyes and shell-like heads with three fins. Once a warlike race, they embraced peace a thousand years before the 20th century.

When their world was devastated by accelerated radio waves sent from Dr Louis French's radio telescope, the Morraxians swore revenge on Earth. The Third Doctor arrived and stopped their plans, then worked with them to construct a time reverser to undo the damage the radio waves had caused. (COMIC: Is Anyone There?)