Kronan are giant rock aliens.
History
Thor: The Dark World
On Vanaheim Thor alongside Fandral, Sif, Volstagg and Hogun are fighting off Marauders in the final battle to restore the Nine Realms into peace. Near the end of the battle a Kronan walks on to the battlefield killing an Asgardian and entering a cirlce of Marauders with Thor in the middle. Thor jokes with the Kronan and then throws Mjolnir at the Kronan, killing it in one strike. The Maruders then surrender and the battle is over.
Guardians of the Galaxy Vol. 2
To be added
Thor: Ragnarok
To be added