Devonians

The Devonians are a fish-like alien race that appears in the IDW comic book series Godzilla: Rulers of Earth.

Godzilla: Rulers of Earth
The Devonians came to Earth from their homeworld centuries ago and have been living under Earth's oceans ever since. Recent intrusions by the surface-dwellers have infuriated the Devonians' leader, causing him to begin plans to exterminate the human race. The Devonians made an alliance with the Cryogs, agreeing to partition the planet equally between each other after the humans' destruction. The Devonians genetically engineer an army of murderous crustacean monsters they call Destoroyah and send them to Honolulu. Steven Woods manages to drive most of the Destoroyahs off, but upon encountering Godzilla they merge together into one giant demonic monster. Destoroyah badly wounds Godzilla and forces him to retreat. Godzilla later returns with Mothra and together they manage to defeat Destoroyah.

When the Cryogs seek refuge with the Devonians after their ship is damaged, the Devonians seize the opportunity to send their newest creation, the plant monster Biollante, to destroy the ship and end the two race's truce. Biollante kills most of the Cryogs and annihilates their ship, but is attacked by Godzilla. After Godzilla causes a nearby volcano to erupt, Biollante is burned alive and dissipates into energy spores that retreat to the atmosphere. The Devonians then launch an all-out assault on a human naval fleet using their mind-controlled monsters Titanosaurus, Manda, and Gezora. Unbeknownst to the Devonians, the Cryog leader has survived Biollante's attack and has taken the form of a Devonian and given the humans information on how to destroy the Devonians' capital. The Devonians send the revived Destoroyah along with their other monsters to fight off Godzilla and the human military, but their forces are ultimately defeated and their capital is decimated.