Sand King is the ruler of the sand kingdom of "Jumanji" and collects various treasures for himself, seeking the chest of magic gold coins that curse anyone that touches even just one.
The Sand King is a greedy miser, who covets treasures for himself (ironically, being made of sand references the common trope about treasure being buried in the sand). Despite having an impressive hoard, his greed is insatiable as he desires the magic chest of cursed gold. He is very quick to accuse and has a dislike of outsiders, citing that the three humans intended to steal his treasure, when they didn't. When he finally acquired the magic chest, he touched a Gold Coin and became even more aggressive due to transforming into a Raging Bull.
In The Magic Chest, after Peter falls down a hole and discovers a treasure chest of glittering Gold Coins, he hides them in his backpack to take home. Alan and Judy fall down into the pit too and they enter an underground room where they find a lot of treasure and come face to face with the Sand King himself. The Sand King is self-obsessed with collecting treasure and is currently looking for a magic chest with Gold Coins. The Sand King is very untrusting of the humans, believing they have it, and has his Sandmen chase them. Peter, Alan, and Judy fall through quicksand and return to Brantford leading them to believe they solved their clue.
In Brantford, the trio discovers that anyone who touches a coin turns into an animal and if they don't get the chest and the coins back, the town may turn into a zoo. They soon fall into the school sandpit and end up back in "Jumanji" again, where they encounter Trader Slick. His comments cause them to realize that if they toss the chest in the ocean, the curse will break as that's what their clue means, but Slick steals it. Peter forces him to give it back, but he secretly steals the coins before doing so. The three go to throw the chest into the sea but are caught by the Sand King who discovers the chest is empty. They escape and run into Slick who's been cursed as well and he gives up the coins. The Sand King and his drones confront them, but Peter destroys the drones and seemingly kills the Sand King with his new squirt gun. Afterwards Peter tosses the chest into the ocean and the curse is broken restoring everyone affected by it to normal. Peter's clue is also solved and they return home.
In The Ultimate Weapon, despite his past defeat, the Sand King was invited to Trader Slick's auction for the Trans-Vector. The Sand King attended the auction to presumably add it to his collection, as well as the other hostile "Jumanji" inhabitants uniting over their common hatred for Alan Parrish, Judy, and Peter Shepherds. The Sand King didn't participate in the chase to retrieve the Trans-Vector.
- Regeneration: The Sand King is made of sand, therefore, if his body falls apart, his minions can pour sand onto missing sections to restore his physical form. Unlike Mud Boy, the Sand King and his people don't appear to be able to grow in size by absorbing more of the stuff they're made of.
- Strength & Speed: As a Bull, the Sand King obtained the abilities of a Raging Bull.
- The Sand King says nothing in The Ultimate Weapon, either because his voice actor was unavailable or the writers didn't include him in the chase for the Trans-Vector.