Initially, gizoids were known from only a single specimen, Sonic Battle's Emerl, who was studied by Professor Gerald Robotnik. However, in Sonic Chronicles: The Dark Brotherhood, it is revealed that the robots represent an entire manufacturing line of military ordinance. The Nocturnus continue to utilise gizoids inside the Twilight Cage.
Artificial soldiers were developed by the Nocturnus around four thousand years prior to Sonic's time, as Imperator Ix's people vied for control of the ancient world against Chief Pachacamac and the Knuckles Clan. Marching out of the factories within the Nocturne citadel, the prototype Gizoids fought at the forefront of the Nocturnus armies, and (according to Ix's hyperbole before the final boss in The Dark Brotherhood) turned the tide of the war against Knuckles' ancestors. Gizoids' strength lay in their ability to flawlessly mimic their enemies' attacks, allowing them to become more skilled in combat with every vanquished opponent. Indeed, in the Nocturnus' ancient language, the word gizoid means "everything" (Gerald's Journal #3, Sonic Battle), referencing the robots' ability to copy any technique or incorporate any weapon into their own systems.
After Perfect Chaos obliterated their rival brethren, the Nocturnus Clan enjoyed a free (if brief) reign over Sonic's world. Robotics research and development didn't stop during this time; the pinnacle of Gizoid science in the ancient world came in the form of Emerl, a robot with the ability to absorb Chaos Emeralds. Thousands of years later, and a whole dimension away on the Kron Colony, Nestor the Wise conjectures that it was precisely this breakthrough development which attracted the attention of Argus, and led to imprisonment of the Nocturnus echidnas in the Twilight Cage. Rightly or wrongly, the Nocturnus were removed from Sonic's world shortly after Emerl's creation.
Excluding Emerl, every single Gizoid under Nocturnus control was transferred to the Twilight Cage in the Argus Event, along with the Nocturne and (apparently) most - if not all - of Nocturnus civilization. Imperator Ix continued to use the robots as the echidnas subjugated the other races of the Cage, and advanced Gizoid models remain a central part of the Nocturnus army when Sonic and friends arrive there during Chapter 7 of The Dark Brotherhood.
|Sonic the Hedgehog (game series) characters|
|Heroes||Sonic (Super, Hyper, Darkspine, the Werehog, Excalibur) | Tails (Super) | Knuckles (Super, Hyper) | Amy Rose | Cream | Blaze (Burning) | G.U.N. Commander | Emerl | Silver (Super) | Marine | Shade | Lumina Flowlight | Chip | Shahra | Knights of the Round Table | Caliburn | Yacker | Sticks|
|Anti-heroes/ Neutrals||Shadow (Super) | Rouge | Espio | Charmy | Vector | Mighty | Ray | E-102 Gamma | Chaos (Perfect) | E-123 Omega | Bean | Bark | Jet | Wave |Storm | Merlina | Illumina|
|Villains||Dr. Eggman | Metal Sonic | Mecha Sonic (Super) | Metal Knuckles | Tails Doll | E-Series | Fang | Gemerl | Eggman Nega | Battle Kukku Army | Biolizard | Black Doom | Ix (Super) | Void | Iblis | Mephiles | Solaris | Dark Gaia | Witchcart | Erazor | King Arthur | Orbot | Cubot | Lyric|
|Teams||Sonic/Heroes | Rose | Dark | Chaotix | Babylon|
|Other||Gerald & Maria Robotnik | Big | Chao | Tikal | E-101 Beta | Heavy and Bomb | Flicky | Animals|