An aquatic creature, Raiju invokes a Galapagos iguana and Crocodile in appearance and behavior. Broad shouldered, Raiju is heavily armored along its back and head. The "head" itself is a tripartite jaw that encases the creature's bioluminescent head for protection. Its feet are bent, enabling it to swim quicker through the water.
Raiju emerges from the Breach along with Scunner and Slattern to defend it from Gipsy Danger and Striker Eureka. When the Jaegers arrive to bomb the Breach, he proceeds to stalk the Jaegers from the darkness during their approach to the portal. Raiju assists Scunner in attacking Gipsy Danger, tearing its right arm from its body before it (Gipsy Danger) can kill Scunner.
As it circles back for a second attack, Raiju runs headfirst into Gipsy Danger's Chain Sword, which, combined with the speed at which he was swimming, bisects him from head to tail. Gipsy Danger initially attempts to use one of the halves of Raiju to enter the Breach, but abandons it, choosing to use Slattern's body instead as a shield as it enters the Breach.
- Main article: Raiju/Appearances
- Raiju's nickname during development was "Croc".
- According to Tendo Choi, Raiju was the fastest Kaiju on record prior to the appearance of Slattern.
- The appearance of Raiju, specifically its head, may be an homage to the Ultraman monsters, Gabora and Suppitol, who also have a protective false heads which they use to protect their real heads from their enemies.
- Raiju's name is a bit of a misnomer, as the Raiju of Japanese mythology was a creature with a broad range of appearances such as a wolf, cat, weasel, or fox. It was the companion of Raijin, the Shinto god of lightning.
- Raiju is a playable DLC character in Pacific Rim: The Video Game.
- Raiju is the heaviest Category IV Kaiju in Pacific Rim.