InGen's chief scientist, Dr. Henry Wu, was fascinated with the possibility to create entirely new species by gene mixing, ever since he learned that the inclusion of frog DNA had given the dinosaurs the ability to switch gender. On May 21, 1997, he created Karacosis wutansis, a hybrid plant. On April 5, 2009, another hybrid was created.
Years after opening, Jurassic World's success was lower in 2011 unlike the previous years of its operation. Simon Masrani attended a meeting on April 4, 2012, in which the board of his company unanimously desired a new attraction for Jurassic World to satisfy investors. After he had gotten out of the meeting, Simon emailed Dr. Henry Wu his approval to create a new species.
Twenty years after the events of the original film, Dr. Henry Wu, Commander Vic Hoskins, and their research team, InGen, formed a new species by using the genes from other dinosaurs to spark more attention of their successful park Jurassic World in Isla Nublar, which resulted in the hatching of the Indominus rex. Of course, they originally wanted to have two Indominus Rex, but after they hatched, the older one cannibalized her sibling before being placed in her enclosure. After being displayed to Claire Dearing (the park's operations manager) by Simon Masrani (CEO of Masrani Global Corporation and owner of Jurassic World), Masrani requests that he would like Owen Grady (a Velociraptor trainer and the main protagonist of the film) to inspect the Indominus to ensure the park's safety.
Owen and two of the staff arrive at the Indominus enclosure, only to find out that she has escaped by scaling the wall. However, it turns out that the Indominus has actually faked her escape and ambushed the three inside her enclosure, with Owen barely escaping. The two staff, however, were grabbed and eaten by the Indominus, who escaped her enclosure and is sent loose on the park.
Ambushing the Soldiers
Going against Owen's advice to take down the Indominus, Masrani sends in an ACU unit to stop the Indominus' rampage, but the hybrid used its camouflage ability to ambush the team, resulting the deaths of many of the men while the remaining ones fled.
Attacking Zach and Gray Mitchell
Realizing that this has gone out of hand, Claire shuts down the northern area of the park. Zach and Gray Mitchell, Claire's nephews were in a gyrosphere checking out a small herd of Ankylosaurus on the restricted area, but encountered the Indominus, who then kicks the gyrosphere right to the ankylosaurs, causing them to panic and damaging the gyrosphere in the process. During the time, the Indominus manages to fight one Anklyosaur before turning her over on its armor and decapitating it.
Afterwards, she proceeded to attack and break the gyrosphere after hearing Zach's phone vibrate on the glass surface of the gyrosphere, nearly killing Zach and Gray. However, the two escaped by running away from her and jumping off a waterfall to safety, leaving the Indominus to find new prey. As they search for the boys, Owen and Claire soon learn that the Indominus has killed several Apatosaurus without devouring them, realizing that she is killing for sport rather than for food. They enter the old visitors' center, only to be brought a fierce welcome arranged by the Indominus. Fortunately, the two manage to escape alive.
Deciding now that the Indominus is too dangerous to be left alive, Masrani decides to take matters into his hands. He and a couple of InGen personnel pursue the Indominus in a helicopter, but the hybrid ruptured into the Jurassic World Aviary, releasing all the Dimophordons and Pteranodons in the enclosure and causing them to attack Masrani's helicopter and let it fall into the aviary, killing Masrani and the personnel in a brutal explosion.
This action caused the visitors to be attacked by the pterosaurs on Main Street, as well as a few infantile dinosaurs to be taken as prey. This also resulted the death of Claire's personal assistant Zara Young, who was attacked by a Pteranodon on the Jurassic World Lagoon before the two are devoured by the Mosasaurus, named Mosy.
Manipulating the Velociraptors
Following Masrani's death, Hoskins takes over Jurassic World and plans to use Owen's Velociraptors (Blue, Echo, Delta, Charlie) to fight back against the Indominus, which Owen reluctantly tags along. However, Owen soon learns that the Indominus had a little of raptor DNA, which allowed the hybrid to communicate with his velociraptors and make them turn against the InGen team. After this, the team opens fire on the Indominus, but the Velociraptors were still on her side, which resulted in the deaths of Hoskins, the InGen team, and the supposed death of one Raptor (Charlie) while the Indominus fled.
Final Battle and Demise
Following the deaths of Hoskins, Charlie, and the InGen team, the three remaining Velociraptors rekindle the relationship between themselves and Owen and help him fight the Indominus, realizing now that the hybrid was only using them for her own purposes and also responsible for Charlie's death (due to her being being blasted by missile by a rocket launcher). Angry for being betrayed, the Indominus smacked Blue against a building column, only to be attacked by Delta and Echo. Unfortunately, the Indominus was too strong and managed to defeat the raptors by throwing Echo into a nearby restaurant's grill, which explodes, and incapacitates Delta by grabbing the raptor and throwing her offscreen (which has led to fan speculation that the latter survived). Knowing that Owen and the Raptors don't have the strength and power to overtake the Indominus, Claire releases a Tyrannosaurus rex (the same one from the original film named "Rexy") from her enclosure to even the odds against the Indominus.
At first, the Rexy has the upper hand against the I. rex, but the Indominus quickly overpowers her. However, before she could kill her by ripping her neck open (similar to how she killed the Ankylosaurus), the surviving Raptor, Blue, arrives to aid Rexy, who then fights back against the Indominus, shoving her near the Jurassic World Lagoon. There, Mosy rises from the water and grabs the Indominus by the neck, and Rexy, Blue, and the humans watch as Mosy drags the thrashing Indominus Rex down to the depths of the lagoon, where the overgrown Mosasaurus devours the hybrid.
Despite the fact that the Indominus is finally gone for good, her actions are what caused Jurassic World to be permanently shut down unless if InGen decided to compensate the damage later on, as all of the surviving humans head onward to the mainland while the surviving dinosaurs are set free in the wild again following the Indominus Rex's demise. Also, with one of her creators, namely Dr. Wu, along with survived Hoskins's men escaped with some dinosaur embryos and data full of dinosaurs DNA that having promising potential for the warfare purposes (presumably along with the Indominus Rex's genetic code), there's still a chance that another Indominus rex just like her would appear in Jurassic World II and start another incident that surpassed her records in Jurassic World, and possibly be more evil and deadlier. The said hybrid could be either Stegoceratops (hybrid between Stegosaurus and Triceratops), unnamed hybrid between a Pachycephalosaurus and unknown theropod species, and unnamed Therizinosaurus (as all of them can be seen on the computer screen near Hoskins when he revealed his true color and reasons of Indominus' creation).
In either way, one thing was clear: Hoskins' intention of the creation of the "Indominus rex" was so he could use her(or at least a clone of her) for future wars alongside variations of dinosaur hybrids that yet to be created, rather than be an attraction.
Though her story in LEGO Jurassic World remain same, there are some changes due to LEGO adaptation intended to more family friendly manner. Noticeably, she never cannibalized her sibling as she was the sole hybrid to be created, and only injured or K.O.-ed her victims instead of killing them outright. Her actions in attacking ACU units and Apatosauruses even omitted, and she is also less antagonistic.
I. rex was first seen to expresses her resentment over her isolation by making a sad angry face out of bones so her observer could understand her pain. Unfortunately, her patience eventually slimmed before Owen and Claire could do something about it, and decided to escape by create claw marks as the bait just like in the film. She then managed to escape by attempted to attacking Owen, Nick, and Ellis. She flung away Ellis over the wall (which knocked the man flat in process) before chasing Nick and Owen, where both managed to briefly distract her with a bunny and some meat. Though briefly distracted, I. rex eventually chases Nick and Owen again, but unable to locate Owen whom covering himself with oil.
While wandering at the field, she stumbles upon Zach and Gray in their gyrosphere and attacking them, which the chase inevitably led them into a herd of Ankylosauruses. The ensuing chase resulting the collateral damage on Gray's gyrosphere by the time everyone arrived in the forest. One of the Ankylosaurus suddenly moves to attack I. rex, in which the boys used this opportunity to defeat the hybrid. Overpowered by her enemies, she angrily destroyed Zach's gyrosphere, but lost both the brothers and the Ankylosaurus as her tantrum on them was just wasting her time. As this version did not kill the ACU soldiers whom sent after her, she instead accidentally put out the tracking device inside her by accident during the fight.
When tracking the brothers into the old visitor center (not long after they left), instead the boys, she encountered Claire and Owen in old visitor center. She then stalks on them, but unfortunately, lost them after they hiding inside the flowers.
I. rex later confronted by Masrani and a couple of ACU soldiers with a helicopter with a minigun when she stumbles upon Jurassic World Aviary. When they firing the minigun on her, she uses a nearby tree as the shield. By the time she did so however, some stray bullets caused the breach on Aviary, causing the fleeing Dimorphodons to hit the helicopter and causing it to crash. Whilst everyone onboard (including injuring Masrani) survived and escaped from Aviary through the door, the unimpressed I. Rex leaves just as pterosaurs inside the Aviary escaped and invaded the park.
With Masrani's incompetence in stopping the hybrid, Hoskins takes over Jurassic World and plans to use Owen's velociraptors (Blue, Echo, Delta, Charlie) to fight back against the Indominus, which Owen reluctantly tags along. However, Owen soon learns that the Indominus had a little of raptor DNA, which allowed the hybrid to communicate with his velociraptors and make them turn against the InGen team. Here, unlike in the film, instead of through blackmailing, she revealed her backstory to the raptors, in which they sympathizes her and lashed out onto the humans due to the Indominus not being treated in the same way as them. Another battle ensues, resulting many of the InGen team ended up injured and one of them nearly devoured by Indominus whom help the raptor. But thanks to Owen and Barry's teamwork, they managed to save ACU soldiers and firing a pepper bomb on Indominus whom tried to devour one of the soldiers, sneezed him out as the humans escaped. The raptors later attack the Medical Vehicle being used by Claire but are stopped by Gray, Zach, and Barry. Being overpowered, the raptors then resort to calling for help from Indominus who was disoriented and separated due to the pepper bomb.
When Indominus approaching the raptors whom managed to surrounded Owen, Claire, Gray and Zach, she was shocked that the raptors changed their mind after Blue chooses to rekindle their relationship. Angered with this, she then fights the protagonist in full force, and even both summons a trail of earth-wave and sonic roar that both avoided by the raptors. Rexy, whom released by Claire entered the fight. In spite of everyone's teamwork, Indominus still a formidable opponent, as she immediately K.O.ed Charlie and Echo by tossed them aside, but didn't realized that she was more closer and closer to Mosasaurus Lagoon. Dependent with the player, Blue can help Rexy to defeat Indominus or only by herself to Mosasaurus Lagoon, which led Mosy to devour her.
Though devoured, she discovered that Zara and a number of Jurassic World employees inside Mosy's stomach. Considering that she was lonely and (presumably) didn't have people to interact with, she decided to join them in playing cards.