The Quake King, AKA Casso Heaven or Casso Storm, is an Equestrian satyr and a member of the evil conquering family of The Storm King. He is one of the members of the family that deviated from weather-based magic by using the raw power of the 4 elements. In his case, The Quake King harnesses the power of earth to crush his foes, claiming to have done things in a similar tone to Geostorm by manipulating global warming itself, has the ability to warp the terrain to his will, control the tectonic plates, create earthquakes, volcanic eruptions, and so on through his Staff of Cassos, converted into a giant warhammer, and seeks anything in the world of Equestria that grants him more to this power. Originally being the mentor to The Undergrowth King, he was powerless to stop him from being disowned as a minor member of the clan. He has since become aggressive to even The Hurricane King for doing so, and is always mean to even him and anyone he meets, being completely cruel and backstabbing to anyone, including his own henchmen, including a golem named Crudder, and his entire army of Rock Ogres.
The Quake King does have the traditional storm clan armor, but because he's so proud of his physical strength, he only wears it to be formal, as apart from miner's overalls, The Quake King is not afraid to show his musled pexs onto the world, whether it wants to or not! The musles unsurprisingly came from weilding the magic-powered hammer, as it is undoubtingly heavy and he really has to be strong to weild it, making him a wild contrast to the Undergrowth King, who is a big fat slob. In being true to the rock element, his skin is rock hard and trying to wound him would be like trying to cut into stone, practicly useless and just leaves you with him laughing at you, thus makes him durable, but not invulerable if you had just the right force.