Invisible Gem Monster

The "Invisible Gem Monster" is a corrupted Gem antagonist that made its debut in "Island Adventure". Sadie destroyed its physical body, thus making it retreat into its gemstone, which Steven bubbled and sent back to the temple.

History
"Island Adventure" The Crystal Gems were searching for the monster at the beginning of "Island Adventure". Later on, the monster attacked Lars, Sadie, and Steven, causing Steven to summon his bubble to protect them. Sadie subsequently defeated the monster by stabbing it through the torso with a spear.

Appearance
As its name suggests, the Invisible Gem Monster's body is invisible, except for its gemstone. Its features become discernible when substances such as mud or water coat its exterior, revealing it to be bulky with a strong build, two eyes, and a mouth. It doesn't appear to have a distinct head or neck. Located on its chest is a cone-shaped gemstone with a slightly elevated base. While the cone portion is a consistent dark blue, the base is separated by an elevation and contains differing shades of blue. The monster appears to prefer walking on all fours rather than upright, although it is unknown if the monster can actually walk on two legs or if it is disabled, damaged, etc.

Abilities

 * Invisibility - The Invisible Gem Monster's primary ability is, as the name suggests, invisibility.
 * Stealth - With its invisibility powers, the monster is skillful at stealth, as the Crystal Gems thought it escaped from Mask Island.
 * Enhanced Strength - It is incredibly strong, with enough power to pop Steven's bubble shield. However, Steven panicked at the time his defenses were breached, so it may not have been the monster's strength inasmuch as Steven's concentration being broken.

Trivia

 * It has the same gemstone placement as Amethyst, on its chest.
 * Despite having hands, the Invisible Gem Monster runs on all fours.