After Sora, Donald, Goofy, and Jack Sparrow interrupt Captain Barbossa's ceremonial sacrifice of Will Turner, Barbossa calls on Pete to assist him. Pete provides him with the Illuminator Heartless, which absorbs the moonlight in the chamber and makes Barbossa invulnerable to attack.
Though Pete summoned another Illuminator each time one was defeated, Sora and his friends manage to defeat Barbossa and chase Pete off.
The Illuminator is a lizard-like Heartless with green skin on its upper body and blue skin on its lower body. Its arms are large and green, each sporting three digits and what seems to be a brown bracelet. Its legs are diminutive and curl up at the tip, and seem to be used more to cling to walls than walk. Its tail seems to be wrapped in bandages and terminates in a large green and blue lantern with red highlights.
It has a green crest lining its spine as well. The Illuminator's head is green and is mostly smooth, except for a twisted, green antenna that sprouts out of its back. Its mouth is full of sharp teeth and it has a red, chameleon-like tongue. The glowing, yellow eyes of the Illuminator are more prominent than most others, and are in fact the only parts of the Heartless visible when it absorbs the light during its battle. The Heartless symbol is in the middle of its forehead.
In Kingdom Hearts II Final Mix, the Illuminator's skin is a blue-green color. Its claws are gold, and its bracelets are yellow. Red and blue are now the most prominent colors on its lantern, with yellow acting as a highlight for the others.
The Illuminator's name is an ironic reference to the word "illuminate", which means "to shine light on", the exact opposite of what the Illuminator does in battle.