|First appearance:||Jumborg Ace episode 1 "A Gift From the Emerald Star"|
|Latest appearance:||Jumborg Ace Episode 21: "Mystery! Monster Graveyard in Space"|
Subtitle: Colossal Arm Monster (巨腕怪獣 Kyowan Kaijū)
- Height: 65 m
- Weight: 50,000 t
- Origin: Space → Okutama
King Zaigrasu is the first of the monsters dispatched by Anti Go-Ne. Anti Go-Ne created him using a lizard from Okutama mountain. He tried to destroy the Okutama dam, but retreated when PAT attacked. Later, he came to Tokyo Bay and appeared in the industrial area, this time, even Pat's attacks could not hinder him. Jumborg Ace transformed to confront him. King Jaigras started using his powers on Jumborg Ace, in the end he was decapitated by Jumborg Ace using the heading killer.
- King Jaigras' suit would later be modified for the Fireman kaiju Blacker.
- King Jaigras' tail would later be reused for the Ultraman Taro kaiju Okariyan.
- King Zaigrasu is one of the five monsters used in the Grave Yard in space to fight Jumborg Ace, appearing as Ghost King Zaigrasu, while Wutan attacked Earth.
- King Jaigras was originally named Lizard King but was cut for unknown reasons.
- Since all of Jumborg Ace's monsters have reused or modified roars, King Jaigras has a reused Magular roar.
- Design: Yoshiaki Yoneya
Powers and Abilities
- Flames: King Jaigras can fire a deadly stream of flames from his mouth.
- Smokescreen: King Jaigras can breathe smoke from his mouth.
- Strength: King Jaigras boasts superhuman strength.
- Tail: King Jaigras can strangle enemies using his long tail.
- Fangs: King Jaigras has teeth stronger then diamonds.