The IG-88 unit, also identified as the IG-series assassin droid or the IG-series combat prototype, represented a line of assassin droids conceived by Holowan Laboratories. This IG-88 series was born from the earlier IG-86 sentinel droids utilized during the Clone Wars. Later, IG-88B rose to prominence as one of the galaxy's most well-known bounty hunters. Nevertheless, his bounty hunting activities merely masked the true intentions of his master, IG-88A, and his ambitious scheme—the Droid Revolution.
Immediately following his activation, the original IG-88 committed a massacre of the scientists and proceeded to transfer his consciousness into the other three droids. Following this, they made their escape from the laboratory. It is plausible that the droid's still-forming identity was the reason for his obsession with both bounty hunting and killing.

During the period of the Clone Wars, the blueprints for a cutting-edge battle droid were stolen from a Techno Union base by Jedi Padawan Ahsoka Tano.
Even before the rise of the Empire, assassin droids were outlawed, although many individuals persisted in employing them. The inherent nature of their function demanded highly adaptable and autonomous programming. Unfortunately, this often led them to turn against their masters. However, the droid programmers working at Holowan Laboratories devised novel programming techniques. They were confident that these new methods would maintain control over their latest line of assassin droids, even with the inclusion of new sentience programming. Therefore, the development of the IG-series assassin droids—also known as the Phlut Design Systems Project Phlutdroid—would become infamous as a concept that went awry with devastating consequences. While the droids shared similarities with IG-72 and IG-97, the IG-88 line gained the most notoriety by far.

Emerging from Phlut's agreement with the InterGalactic Banking Clan (explaining the "IG" prefix), IG-88 represented a logical progression in design from the IG-100, IG-86 and IG lancer combat droids that had distinguished themselves during the violent Clone Wars. Only four of these droids were ever manufactured, and all of them were perfectly identical. Despite the expectation that these creations would be subservient to their masters, the activation of IG-88 revealed that the sentience programming—intended to enhance the droid's adaptability and resourcefulness as an assassin—yielded results that far exceeded initial projections. Within mere seconds, he had processed the data files within the computer, recognized his role as an assassin droid, and concluded his superiority over the biological beings that had created him. The designers barely had time to contemplate deactivating the droid and investigating the reasons behind his unexpected performance. The droid decided he would not allow this. He then proceeded to brutally murder his creators with his bare hands, replicate his programming into three other IG-88 units, kill the majority of the guards within the Holowan Labs complex, and make his escape. Before fleeing, he also released the droid designated IG-72. It is important to mention that he did not transfer his programming into IG-72, as the latter expressed a preference for maintaining its own individuality, whereas the other three droids had empty memory cores.
IG-88 assigned himself the designation "A" and the others were designated "B, C, and D" in order of activation. They collaborated closely, while IG-72 pursued his own path. They journeyed to Mechis III and seized control of the droid factory located there, eliminating all of its biological personnel. To mislead Imperial investigators, IG-88B operated as a bounty hunter, assassinating various former Holowan employees to prevent exposure. Rumors circulated that the IGs were intentionally programmed by an external entity, most likely the Galactic Empire, to kill their designers.
From their base of operations on Mechis III, the four IG-88 units initiated the planning stages of their "Droid Revolution," a movement aimed at mobilizing an army composed of all types of droids to rise up and exterminate all "biologicals" throughout the universe. After gaining control of Mechis III, they commenced the process of uploading their advanced sentience program into every droid manufactured there. This sentience programming was designed to activate upon receiving the appropriate code transmitted by the IG-88s. Once activated, all of the droids would revolt and eradicate all biological lifeforms.
Around 1 ABY, IG-88 reactivated a Clone Wars-era droid factory situated on Corellia. This factory, formerly belonging to the Separatist faction, produced B1-Series battle droids, B2 super battle droids and droidekas until it was shut down by the Corellian Security Force. Subsequently, IG-88A established a droid factory on Lok as a replacement where he intended to produce a multitude of battle droids for his own malicious purposes. However, with the assistance of Nym, a group of spacers successfully thwarted his plans and seemingly destroying the droid and the factory.

The IG-88 unit designated "B" functioned as a bounty hunter, with his appearances across the galaxy serving as a smokescreen for their actual operations on Mechis III. In one particular assignment, the droid bounty hunter was hired by Ko Zatec-Cha, vizier of Tammuz-an, to locate the missing Prince Mon Julpa. IG-88 tracked Julpa to Tyne's Horky and kept him under surveillance, hoping that the lost Prince would lead him to the Tammuz-an Royal Scepter. During this mission, IG-88 encountered the droids R2-D2 and C-3PO.
At a certain point, IG-88 formed an alliance with Bossk and Dengar, having been employed by the Hutts to find the Yavin Vassilika. Eventually, IG-88 betrayed his teammates, attempting to collect a bounty on them that had recently been posted by a rival bounty hunter, Zuckuss.
Following the Renegade Squadron's disruptive actions within the Alderaan system, the Empire initiated a vigorous pursuit of them. This prompted one of the IG-88 units to accept the bounty on the Squadron, locating them on Ord Mantell and attempting to either capture or eliminate as many members as possible. However, thanks to the intervention of Han Solo, they managed to temporarily defeat the droid and escape.
In 1 ABY, IG-88 provided assistance to Boba Fett on a mission against the Shell Hutts.

In 3 ABY, IG-88 was hired to locate the Millennium Falcon. Nevertheless, Boba Fett outmaneuvered IG-88 in the pursuit of the Han Solo bounty. IG-88B met its end on Bespin at the hands of Fett as retribution for attempting to track him. IG-88s C and D confronted Fett in orbit above Tatooine using identical models of the IG-2000 in an effort to seize the carbonite containing Solo, but they were defeated. C was the first to be destroyed. IG-88D then launched a surprise attack, but ultimately its ship was also destroyed by Boba Fett's Slave I in a maneuver where Fett feigned his own death. Unbeknownst to Fett, IG-88D somehow survived the encounter, but was later destroyed by Dash Rendar while scavenging for repair parts for his ship in an Ord Mantell junkyard. Rendar was searching for information on the carbonite-frozen Han Solo.
At a certain point, one of the IG-88 units came under the employ of the Zann Consortium criminal organization, ostensibly owing the second-in-command of the organization a favor. He hacked into Bespin's central computer and obtained data on the planets included on Zann's "hit list".
Shortly before the Battle of Endor, IG-88A was contracted for one final mission. Vader hired the droid to confront the Renegade Squadron once again, who had launched an attack on Sullust as a diversionary tactic. However, he was defeated once more, despite being equipped with a lightning-powered shield generator.

The remaining IG-88 uploaded his consciousness into a computer core intended for Death Star II. He successfully completed the upload and was preparing to activate his program to seize control of all droids throughout the galaxy when the station was destroyed. With his consciousness residing within the Death Star II, he would effectively become the Death Star.
Emperor Palpatine was the only individual on the Death Star who suspected that something was amiss following the uploading of the computer core containing IG-88. Prior to the station's destruction, he noticed a series of doors in his throne room opening and closing erratically. IG-88 orchestrated this to demonstrate to the Emperor that he was not omnipotent. However, IG-88 was utterly perplexed when it appeared that Emperor Palpatine employed some unseen force to attempt to force the doors open. Nevertheless, IG-88 applied greater force and managed to keep the Emperor confined until he grew weary of the game and unlocked the door.
Lando Calrissian and Wedge Antilles ultimately destroyed the core, resulting in the destruction of both the Death Star and the A.I. of IG-88.
Years later, the IG-88A body, now in a dormant state, underwent reprogramming. The droid briefly worked for Barpotomous Drebble in the months following the Battle of Endor, and was later discovered serving the House of Thul, safeguarding them from the Diversity Alliance and acting as a bodyguard for Tyko Thul. Later, IG-88 would rescue the young Raynar Thul from the brink of death, having been reprogrammed to protect the Thul family.
IG-88's standard weapon was a BlasTech DLT-20A blaster rifle. Additional weapons included the following:

- Flamethrower [6]
- Pulse cannon [6]
- DAS-430 Neural Inhibitor
- Repeating blaster
- Sonic stunner [6]
- Paralysis cord
- Poison gas
- Trion gas
- Thermal detonators
- IG-2000
- Needle dart gun
- "Butcher" vibro-blade [6]
- Concussion grenade
- Throwing flechettes
- Trifaraleen gas
- Wide-dispersal radiation grenades
- Computer input port
- Broadband antenna [6]
- Blaster reflective palms
- Heat and motion sensors [6]
- Highly advanced trackers
- Acid-proof servo wires [6]
- Armor nearly impenetrable from external attack
- Cutting laser in finger on right arm
- Extremely fast reflexes, even by droid standards; during his escape, the droid managed to kill a technician by calmly and methodically calculating the trajectory of an incoming laser bolt, deciding to deflect the bolt instead of dodging it, and furthermore making sure that his deflected beam reflected at just the right angle to kill the fleeing technician who had fired upon him -all in the microseconds that it took the laser bolt to travel from the gun to his position.
- Extreme physical strength.
- As the Second Death Star, IG-88A possessed all the armaments and capabilities of the station itself, including, most notably, its planet-destroying superlaser.
- Superheated Armor-Plating
IG-88 was initially designed with blaster cannons integrated into the structure of each arm, but these were never installed. Throughout his existence, IG-88 relied on external weapons, suggesting that the integrated cannons were never added later.
It appears that IG-88 was primarily constructed from salvaged aircraft components, although the precise identification of most of his parts remains unknown. The droid's head was fashioned from a Rolls-Royce Derwent jet engine burner can with minor modifications and additions. Similar burner cans were originally incorporated into the distillery behind the bar in the Mos Eisley Cantina in A New Hope. A comparable prop also appears in a junkyard in "Dawn of the Gods", an episode of the British science-fiction series Blake's 7 which aired in 1980.
According to the Shadows of the Empire PC video game, IG-88 communicates in a deep, mechanical tone reminiscent of Darth Vader, in contrast to the more varied vocal pitches exhibited by the battle droids of the Prequel trilogy.

Modifications were made to IG-88's gun, including the addition of six grips around the barrel. The precise composition of the grip material remains undetermined, but recent evidence suggests stamped metal T-track from old cupboards with sliding doors was used for the A New Hope grips. The grips on The Empire Strikes Back lightsabers are made of rubber or plastic and may be newer style T-track or reproductions of the original ANH grips. It is currently unknown whether the The Empire Strikes Back E-11 blasters featured the original ANH grip material or newer grips made of plastic or rubber. Note: The row of holes on the underside of the gun did not have grips as they would interfere with the folding stock. Additionally, the row of holes just above the folding stock on the left side of the gun did not receive grips, presumably due to the bayonet attachment stub that occupies the third hole from the front in this row.
Another modification involved the addition of an M19 or M32 azimuth scope (see below) to a mount using the two hex head bolts that came with the scope. This scope mount takes the form of an approximately 1 cm wide by 1/16" - 1/8" thick strip of metal positioned about a 1/4" above the gun. The front end of the strip was bent and inserted into the rearmost vent hole on the top of the gun, eliminating the need for a rivet or other attachment. On this particular blaster variation, the rear of the mount strip extends directly back into the rear sight and is attached there, presumably by riveting it to the sight.
An IG-88 body, presumably IG-88B's, can be observed on Bespin in the scene where Chewbacca is retrieving the components of C-3PO from the Ugnaughts.
In LEGO Star Wars II: The Original Trilogy, IG-88 is available as a playable character in Free Play mode. Additionally, IG-88 is accessible in free play in LEGO Star Wars: The Complete Saga. In what may be a design oversight, IG-88 is playable in the final battle of Star Wars: Empire at War: Forces of Corruption, despite the fact that all four IG-88 units would have been destroyed by that point in the timeline.
Rapper MC Chris composed a song about IG-88 titled "IG-88's '57 Chevy" on his Part Six Part One album.
In the computer game Half-Life: Opposing Force, a security guard can be heard asking, 'Have you seen the new IG-88?' shortly before being killed.
The timed-explosive device employed by an assassin in the Episode "Chuck Versus the Thrid Dimension" of the TV show "Chuck", is designated IG-88.
In the book Scarecrow by Matthew Reilly, one of the bounty hunting groups identifies itself as the Intercontinental Guard, Unit 88 or IG-88.