Caesium

Caesium is a Godzilla and King Ghidorah hybrid, and the second of the Periodic Genesis Kaiju (PGK) to come into existence.

Creation
After his 'father', Francium, wiped the ancient Earth clean, he created Caesium, Germanium, Mercury, Boron, Wolfram and Zinc from his own cells, and sent them to terraform the planet and make it suitable for life to evolve there. It was Caesium's task to create the atmosphere.

The Coup
After the terraforming was complete, Caesium grew jealous of his 'father' and his 'brother' Mercury, and how they seemed to hold control over the other PGKs. It was then that Caesium and the others led a coup against Francium and Mercury, killing them both before dispersing throughout the universe. After billions of years, Caesium landed back on Earth to see it teeming with life, and fell dormant, awaiting the time when subjugating the vibrant planet was right.

Periodic Genesis: Dawn of Sepsis
In this comic series, Caesium makes his first and only appearance in Part #3.

Caesium made a horrible mistake in appearing when Sepsis was planning his assault on the planet. After hibernating for centuries, Caesium had assumed a new form, his 'Luster mode'. Off-screen, Caesium was challenged by one of WeegeeZilla's friends, Linkzilla.

During a pause in the fight which had escalated into a stalemate, Sepsis set his plan to eliminate the PGKs in motion, sending Organon to murder Caesium. Stabbing the PGK with his extendable tail, Organon slew the powerful monster without ever having to show his face, and then quickly slipped away, Sepsis appearing as a projection shortly afterwards.

Standard

 * Flight: Caesium can fly at speeds of over Mach 10.
 * Gravity Beam: Caesium can fire a single version of King Ghidorah's Gravity Beams, although this beam is more powerful and can levitate objects.
 * Nuclear Pulse: Caesium can fire a version of Godzilla's Nuclear Pulse, strong enough to melt an opponent's skin if prolonged.
 * Hallucinogen Power: By concentrating, Caesium is able to make foes suffer from visual hallucinations.
 * Luster Mode: By absorbing the Earth's radiation for long enough,

Luster
It should be noted that none of these techniques were ever shown in the comic due to Luster Caesium's swift death.
 * Luster Typhoon: Luster Caesium's most powerful move; The Luster Typhoon takes the form of a spiral version of Caesium's Gravity Beam, and is capable of slicing through opponents.
 * Luster Gain: By continuing to absorb Earth's radiation, Luster Caesium can spontaneously regenerate injuries at a very fast rate.