Pandorite

A Pandorite is a monster-in-a-box found in Super Mario RPG: Legend of the Seven Stars. Pandorites resemble squat, pudgy ghosts that disguise themselves as Treasure Boxes. As such, Pandorites can easily prey on unsuspecting adventurers searching for valuable treasure.

Mario and Mallow encountered a Pandorite while exploring the ghoul-infested Kero Sewers. In battle, the Pandorite proved that it was not only very clever, but that it was also quite powerful. The heroes discovered that Pandorites posses both high physical attack and defense, and equally high magical attack and defense. In addition, almost all types of special attacks are ineffective against the treasure boxes (except, fortunately, for Mario's various Jump attacks). In battle, the Pandorite can wield exceptionally powerful fire magic, including the Flame and Flame Wall spells. The creature also used the attack Scream, inducing the Fear status ailment and cutting an ally's attack and defense in half. Additionally, the treasure chest ghost used the special technique Carni-Kiss, allowing Pandorite to voraciously bite a party member and cause significant damage. When it was not using special attacks, the specter inside the box occasionally revealed himself and assaulted Mario's party. Eventually, Mario and Mallow overcame the Pandorite and continued their adventure.

Fortunately, like real treasure chests, Pandorites are able hold a considerable amount of treasure. After Mario and Mallow defeated the Pandorite in Kero Sewers, the heroes received ten experience points, thirty Coins, a Flower Jar, and a valuable Trueform Pin. This Trueform Pin proved useful in the eventual battle against the guardian of Kero Sewers, Belome. Later in the game, if Mario returns to the Treasure Box that previously held the Pandorite of Kero Sewers, he will receive an additional fifty Coins. In fact, as soon as Mario leaves Pandorite's room, the Treasure Box will be filled with the Coins, meaning Mario can simply exit and reenter the room to claim the additional reward.

Pandorite is, in all likelihood, related to Hidon, Box Boy, and/or Chester, although the creature inside looks like what's inside a cluster.

Trivia

 * Pandorite's name comes from the Greek legend of Pandora. According to the legend, Pandora was the first female human ever created. Pandora, according to the story, opened a jar (named Pandora's Box) that released the world's misfortunes, such as plague, crime, poverty, greed, and war.
 * Pandorite (and its relatives) are the Super Mario RPG equivalent to the Final Fantasy series Mimics, which are also monsters that disguise themselves as treasure chests. Both Super Mario RPG and the Final Fantasy series were developed by Square Enix.  In fact, Mimics appeared in the game Mario Hoops 3-on-3, a Mario-Final Fantasy crossover game.
 * If the player finds a roulette ? chest and gets three different icons, the last "monster chest" encountered will be battled again.