Garnet was first ever formed 5,750 years prior to the series beginning, albeit by pure accident. During the first attack by Pearl and Rose Quartz, Ruby and Sapphire fused together when Ruby tried to protect her from being attacked. Garnet was very shocked and confused the first time around and split within minutes, yet sometime later, she came back together and eventually she decided to permanently stay together as a Perma-Fusion. She joined the Crystal Gems in order to be sure of that after both Rose and Pearl were so open to the idea, and accepted her for who she was.
She was amongst the very few who survived the Gem War on the Rebellion's side, able to avoid becoming a victim of Corruption alongside Rose, Pearl, and Emerald. Once she figured out the end result and finding the other Corrupted Gems, she and the other Crystal Gems took it upon themselves to capture them, as they didn't know how to cure any of them at the time. During this timeframe, she came across Amethyst, and the Crystal Gems decided to keep her. However, none of them really told her about the Gem War, on request by Rose herself in order for Amethyst to be more free, yet Garnet made it clear after a while to Rose that she had to tell her at some point. They agreed they'll tell her after three more years. When Amethyst confronted them about it however, she insisted on telling her the truth. After this incident, she promised to Amethyst that they'll be more open to her from them on. When Rose did eventually pass on to give birth to Steven, Garnet took on the role as leader of the Crystal Gems.
When Amethyst got her gemstone cracked, Garnet and the current Crystal Gems (her, Pearl, Amethyst, and Steven Universe took her to Rose Fountain, only to find that the entire place was infested by Plunder Vines. Garnet stayed level-headed about the situation, and managed to help her team reach the fountain itself. She and Pearl proceeded to go and unclog the water going into the fountain, just to come back and first finding Twilight Sparkle. Wary, she armed herself, only to be told that Twilight saved Steven and Amethyst from said Plunder Vines. After that was properly cleared up, Garnet introduced herself, and figuring out she was far away from Equestria, decided to let them all stay - her and the Mane Six. By next morning, once the Mane Six leave, Garnet suggested to Steven to give them a tour of Beach City, her pretty confident in thinking they'll meet up again. When they got back, and when Discord appeared, she immediately began to question him, though not too comfortable around him, even after he successfully got the Mane Six back home.
Once summer started, Garnet took notice of Steven's involvement with Lapis's Mirror, and she herself tried to take it away from him, only to be stopped when Steven's Portal Key distracted her and the others just long enough for Steven to escape, Garnet stating he was in big trouble. Garnet got Pearl and Amethyst and fanned out to try to find him, just to discover Lapis Lazuli was free. Garnet tried to get to them, but she was too slow and lost them through the portal to Equus. She and the others tried their hardest to figure out where he and Lapis went for the next four days, going to every single Gem location on Planet Earth, until Discord found them again. She got insulted when Discord accused her of being selfish for trying to take Lapis away, her insisting that she placed the team over herself, much to Discord amusement. Garnet tried to get them moving, but instead ended up watching "Daring Do, and the Aqua Gem", finding out where Steven was, and eventually given her portal key.
She got the group over to Ponyville shortly afterwards to find Lapis and Steven, her keeping an open mind and thanking Lapis for being Steven's friend. It took a short bit, but she eventually had Pearl and Amethyst look around Ponyville as she went to The Geode as apart of her missions. When she investigated the Geode, she found Fulgurite inside, and she tried to befriend her, only for her to run away. She got to her though, and after Fulgurite fixed the Geode herself, brought her back to the Crystal Temple. Her next mission with them brought her back to the Fountain, finding it infested with Poison Joke this time, and she became one of those infected by it, resulting in her being too weak to even lift a spoon. She was forced to stay behind, much to her dismay and her not wanting anyone else to know about it, just to find that the Spider Monster had came to their Temple. She tried to fight it, but found herself getting hurt more than the spider, and she had to hold it off until the others came back to save her.
Her adventures in Equus didn't stop there: her visiting Rainbow Falls for the Equestrian Games tryouts to help in the "accidents" reoccurring, lending a hand when Discord arrived to Ponyville sick and needing assistance, and getting the communicator rebuilt found by Blue. When Steven told them about what he saw in Warp Space, Garnet decided to ease Steven's nerves by checking the various locations, despite also having her doubts like Pearl and Amethyst did. She did eventually go back home once all the areas had been checked, and Rainbow Dash and Fluttershy staying to guard the Galaxy Warp.
When Pearl ended up "discorded" by Discord, she went on to call for a search of Beach City, although by the end she revealed that she knew all this would happened, and figured out Discord's true intentions behind it as a way to help Pearl out rather than harm her, though she still whacked Discord for making everyone worried. Things began to escalate however when Steven went missing, supposedly to bring Rose Quartz back, and she immediately went off with everyone else to get him, arriving just in time to find Steven become a victim of Corruption. This problem was so hard on her that she couldn't stay together, and ended up splitting back into Ruby and Sapphire, much to Sombra's delight. Garnet didn't return until after Ruby freed herself from her curse, and she immediately went off to fix the mess he had made. When heading to the Lighthouse, she found Tirek there, and she went to fight him, unfortunately getting sucked clean of her power in the process. Once she returned, and the problem mended, she brought Steven back to the fountain in hopes of curing him, and giving her gratitude towards Nephrite for finally curing him.
After a long day of play, Garnet got Steven off to bed, telling Steven that he'll have all day tomorrow to play and it was time for "cutie pie" to get some sleep. She found Steven unable to wake up the next morning, and after futile attempts to wake him up, brought him to Equus for an answer. She found out about Lucid after talking to Celestia and Luna, and she went with the others into the Dreamscape in order to get him back. She tried to go through Lucid's numerous puzzles and traps, and once she did finally find Steven, she concluded that they had to go in even deeper in order to get him out. This was when she ended up split again. When she did finally come to in the real world, she was given a picture and figured out Lucid's true motives that he just wanted to help Steven in his own way.
Sometime later, Garnet went back to the Crystal Temple and waited for Flint and Jade to return. Once they did, Garnet explained to them how they've been capturing various corrupted Gems, in hopes of finding a cure for them, and that she wanted them to cure them, just to get a rather abrupt no from Flint, reminding her how dangerous that was. The only Gem she got from that was Diopside.
She gathered up the group sometime later for a mission in the Prime Kindergarten, though during the mission she had to confront Jasper after being constantly talked down to, and her trying to get her to listen. That only stopped when a Cluster Gem found them, and during a fight, she and Jasper fused, again by accident, and formed Carnelian to defeat her. She tried to relax after that fact, when Lapis Lazuli found her and talked to her about Homeworld and Blue Diamond. It was then that she got her Future Vision of the Crystal Gems and Homeworld coming to terms and living peacefully, a goal of which that got her very excited and happy to complete, to the point of tears of joy. She got this mission to the others the next morning, and after explanation and proper planning, began works on the Galactic Ray. It was during the first stages of the project when Peridot confronted her about being a Perma-Fusion, and Garnet offered to fuse with her to show her, though she playfully brushed it off when Peridot began to freak out about it. She isolated herself from there and met up with Jasper, getting her to understand her situation just before they found the Jet Monster. It wasn't until they formed Carnelian again did they win, and it was found out that she knew about it, but didn't want to ruin the fun.
She and the others went off to the Strawberry Battlefield in order to get some weapons for the trip, when she had her first encounter with Kyra. She made it clear to him after he accused them of being thieves that they were indeed the Crystal Gems, and kept an eye on him, growing suspicious over him and his intentions. Discord eventually came across her again, this time giving his so-called "friendly lessons" to Peridot, Garnet foreseeing this coming this time, and bringing Peridot over to the Sky Arena. She told Peridot this was where the first battles took place, and any Gem fighting there, regardless of which side, is proved to be warriors, which inspired Peridot to ask her for some training, as Garnet hoped. She split apart shortly afterwards for Ruby to train her, and once she came back, claimed she will be training Peridot herself.
When winter first started, Garnet found Jasper inside the Barn House, and prompted her to come on outside into the snow. She tried giving Jasper a good time, and she decided to begin a snowball fight with her. Their snowball fight escalated until they almost hurt Blue, Garnet deciding Jasper had one so they wouldn't hurt anyone else. After their fun in the snow, she continued the process of building the Galactic Ray (getting involved in the Talent Contest of the Gifted as Sardonyx).
Homeworld Arrival Arc
Upon completion, Garnet got everything together, making sure that Kyra was staying behind whether he wanted it or not and Discord lending her a Diamond Communicator, and began to head off on her way to Homeworld. On the way, she found Peridot, and asked her to help her make a call to Homeworld for her. When Blue Pearl saw her, Garnet informed herself as Sapphire, and got to talk to Blue Diamond about their arrival. Before she left the room after the call, she told Peridot that she didn't have to worry about telling them anything if it meant it was important. Upon arrival to Homeworld, Garnet actually split herself up to show Sapphire to Blue Diamond directly.
Garnet reappeared just before the duel between Jasper and Rupee, and was in attendance during the duel next to her Diamond when she got a vision of Kyra's talk with Discord, growing concerned for his involvement. Those worries were confirmed when he showed, and Garnet intervened in the duel in order to save Yellow Diamond. After the incident, Garnet found Kyra outside the Diamond Cities, and they both agreed to not lie to eachother. She first asked him how he got there, and explained next of her future vision she so wanted to happen. After hearing his explanation, and his reasoning behind her previous Duel with the Diamonds, she made it clear that his plans were very flawed and hypocritical, and that if he would've told them straight up they would've helped him. She stated next that he had a lot to learn, before going back to Blue Diamond City to get everything ready for the Osicone's arrival.
She arrived back to the Diamond City, straight to Blue Diamond, and asked her about the Osicone before the first tremors occurred. She shared her vision of the Osicone with Blue Diamond, and once making that clear, went with the other Gems to confront it as she left the Mane Six and Steven behind to find Kyra, and for their safety. She eventually found it and tried to fight it, but in the process got split up in one hit. She didn't reappear until after the fight took place, reforming after the Crystal Gem Mega-Fusion split apart. After the ceremony, she agreed to let Jasper, Peridot, and Emerald stay with them.
Garnet got word after a while of Cranky Doodle and Matilda Doodle's wedding, and she found the concept of a wedding very lovely. When told of how much trouble though, she made it very clear and very important that this wedding would come to pass, saying their love was at stake, and that was enough of a reason to even get involved at all. Once they got there, she and Jasper went off outside of Ponyville to confront the Bugbear, which Garnet predicted, and it took little time for it to be driven off, securing the wedding. She arrived at the wedding herself, finding Peridot, and Derpy Hooves coming with the good luck package, giving them a hint at their final piece of the puzzle before the wedding started.
During Velvet Sugar's visit, Garnet had the idea of her involvement and supposed "cheating" according to Pinkie Pie, though she didn't come in to clear things up until after Steven told her Pinkie would be behind. Her excuse was that she liked the sweets Velvet had made.
Sometime after, she began to sense involvement over at Jersey Quarry, and she tasked the Crystal Gems to go and investigate. She was found by Time Jumper, and quickly dealt with, along with the rest of the Crystal Gems with the exception of Amethyst. She didn't return herself until after a few weeks, and as a present by Blue Diamond, Discord, and Celestia, was presented with some signature Warp Pads that lead back to Homeworld.
During the celebration for Lapis's Anniversary, and on discovering Stevonnie, Garnet was the most excited to see this happen, and she made it a point for her that she was an experience and they should make it a very good one. She tried to make it clear to Flint later that this was alright for them, her getting extremely frustrated with him, until Jasper came in and stopped it. She expressed how proud she was for Steven and Connie Maheswaran, and how exciting it was that a fusion like her existed at all. She gave her and Lapis a happy birth-iversary sometime afterwards. She was found later by Blue Pearl, and during her visit Garnet brought her to the Lighthouse, only to return with her and finding Zappy. Seeing how stressed Blue Pearl was for seeing Zappy, Garnet got her back home as Zappy was watched by the others.
When Steven decided to do his first solo-mission, Garnet took the time to calm Pearl's nerves by showing her a future vision of the end result. She spoke to him during the mission through his cellphone, and she told him that he can call them at any time, and that they were all there for him. While happy to see him come back home, she ended up becoming effected thanks to one of Quetzalcoatl's feathers, catching the "Gem Cold". She had little idea on what the disease truly was, but she gave Steven a future vision as a way to help him find the Healing Crystal.
She warmly welcomed in Bismuth on her return to the Crystal Temple, enjoying her company just like old times and getting her more comfortable to the world after her time gone. During her watch though, she and Flint laid witness to Quetzalcoatl, something she didn't predict on but decided to just say she did and move on.
Garnet ended up disappearing after this and throughout most of the Season 4 finale, her only appearing again when Sapphire was freed and healed before the fight occurred within the White Diamond Space Station throne room.
Garnet joined a few of the ponies one night for some star-gazing, when she ended up coming across Navy. Seeing how damaged she was, she helped bring her back to Twilight's Library, and got the information about Aredox, and the rest of the Ruby Squad. She got the team together to go, deliberately leaving a few behind. During the flight off to it, she got word from Navy and Peridot about Applejack, Amethyst, and Steven's capture, and arrived to Aredox in little time.
Upon arrival, she readied to go in, but had to fall back thanks to the coming of Agate patrols, and she had to wait over by the ship as Bismuth rounded everyone up.
Throughout the winter, Garnet tried to relocate Malachite, but still not having too much luck herself. She took a break from looking and went to the Crystal Temple to find Steven and Jamie, explaining the situation to him. She left out the detail that they were missing so Jamie wouldn't have to worry about her. She expressed her worry over such an unstable fusion to the other Crystal Gems when they got a diamond message from Yellow Diamond, and information regarding The Cluster. She was rather upset at Peridot for not telling them, mainly for the fact it could've gone off and she'd been with them for "over a year and a half" at that point, and while she saved her from being hurt by Bismuth and Flint, she still bubbled her and sent her to the Temple after Star Quartz spoke to her. She decided to leave Amethyst and Steven out of this, as she felt that they had more than enough trouble on their minds as it is.
After a bit, she returned and got Peridot out, mainly because she knew more about the Cluster than any of them did, but she still had her restrained by a leash as they began production on the Gem Drill. Her frustration only got worse when a Rhino Monster began to constantly reappear, no matter what her future vision dictated. It wasn't until Watermelon Tourmaline appeared and destroyed the Gem Drill did she find out about Pearl's involvement. She showed her anger towards her, extremely upset for her jeopardizing their plan to save Earth, regardless if she meant to or not, and had her put under lockdown alongside Peridot. She began to feel a little questionable about it later on however, especially since it resulted in Pearl's gemstone becoming cracked, and it only got worse when she realized they went off after the Cluster themselves. Realizing her mistake, she rushed to get them back but arrived too late to stop them. She pleaded with Pearl and Peridot to come back once communication had been given, only to not be given her wish, and she could only stand and wait for them to return from their mission. She was more than pleased once they did, crying tears of joy as she hugged them both. She brought Pearl to the Rose Fountain to heal sometime later.
Relieved and happy, Garnet took some time off from what they've been given, but this was a bit short-lived when she was called up to Homeworld for The Trial against them for the supposed shattering of Pink Diamond and Blue Diamond. Garnet didn't do much during the actual trial, and in the end she and the others were banished from Homeworld, charged for the Pink Diamond case. Sometime later, Lars Barriga told her about Grootslang, and after some looking up in Mushussu's Bestiary, got an idea on where Blue Diamond might've ended up. During that night, she found and confronted Grootslang, who just ruined Lars's dish for Buck Dewey's potluck, and while she didn't manage to catch him, she did plan ahead and gave Lars another dish to replace the one wrecked.
As she tried to figure out Grootslang's whereabouts, she eventually got warning of an upcoming Hurricane heading towards Beach City, and after some consideration, got them to evacuate the city, and the Gems to board up the Temple for the oncoming storm. Even Garnet didn't realize until too late that it was all a trick, the Beach City Flooding occurring instead. She was left shocked, her Future Vision even saying a hurricane was coming, but she regathered herself, stating that the odds caught up with them. She was especially sorry towards Flint, who she forced back earlier, and coined the event to be sabotage. She told the residents that she understood how upset they were at Acid and Cyanide, and that the Gems will get back at them as they rebuild the town.
It took her a while, but they did eventually find out where Grootslang was, but not until after Amethyst, Steven, and Connie were stolen for ransom. She lead the charge in locating Grootslang, but after an unexpected capture, and figuring out the location, Garnet came up with a "Trojan horse" plan, and had the Mane Six give them the other diamonds, which were actually cases for them to hide in. She busted out soon after being placed, and fought Grootslang to get the Gems back. After Grootslang's defeat, Garnet got Lapis Lazuli back to them as a sort of surprise, grateful that they were all there at last.
Garnet was one of the Gems invited back to Blue Diamond City once Blue Diamond had returned safe and sound, Garnet missing her since she disappeared, yet she was found by Pearlis, and it turned out their sentence from the Trial still stood, and they all just broke it. Garnet got the group moving, but was caught outside shortly afterwards. Upon managing to break free, she lead the group away from the threat, her future vision leading them to a drop off down to the Supreme Kindergarten. They explored the kindergarten for a while, and eventually she ran into the Off-Colors group. She saw the group as nothing more than another Crystal Gem group, and after some explaining to them she allowed them to come back to Earth with her, promising they can be free and do what they wished instead of hiding their whole lives. After getting them back, and out of trouble, she got involved in another meeting in regards to both the Cluster and the Diamond Attack described by Rhodonite, beginning the Pink Diamond investigation.
Garnet started her involvement by bringing the Mane Six, and Lapis Lazuli over to Pink Diamond's Palanquin for some sort of clue or indication on the idea. She didn't rush her through her memory, but didn't blame her when she couldn't give them more than what they already knew. She continued trying to figure out this case along with the other Crystal Gems, though during this she figured out about Spinel, which made her especially excited to hear about. It didn't take her very long before meeting the Gem fusion, and joined the other fusions for a field trip planned by Steven to the Peruvian Plains. As they tried to understand Spinel, Garnet made sure that Tiger's Eye didn't say the wrong thing, and in the end concluded that they were perfect for eachother.
Things begin to go downhill for her when Diamond's Dog arrived to take Steven away. After the fact, She and Flint both went out after the Cluster again, and managed to destroy the drill planning to release it. She told Rhodonite about it to calm her nerves before Discord arrived and took them to his Dimension, splitting Garnet up in the process. Once she got back, she reformed and Garnet tried to help Steven out with his issues, reassuring him that she wasn't upset with him for his decision, and suggesting he should visit Ponyville, wishing him good luck once he left. When Bismuth and Lapis left to try and talk to Pearl, Garnet joined the others to try and help, only to find that Pearl had poofed herself. Garnet didn't place any blame onto Flint though, despite him pushing her the whole time to get answers.
Shortly after this, Garnet got captured along with the other Crystal Gems and brought back to the White Diamond Space Station. Garnet remained together, but remained trapped until the humans arrived and freed them. She ended up caught moments later by Aquamarine, and once brought back to the throne room, found out what White Diamond's involvement was in the War, and that it was Garnet in particular who inspired her in the first place, making Garnet both angry and very pressured. She was placed with the others in the Science lab, her forgiving Starlight Glimmer for her involvement in all of this before she learned further about White Diamond's involvement, and finding out the state of everything down on Earth. She learned just how little was left on Earth of their existence, and got her believing that there was nothing to go back for. She got her confidence back sometime after thanks to Fluorite, and with Topaz's help managed to get free. She took to the fight, and during the scuffle managed to help in getting Yellow and Blue free, before they managed to get off the Space Station, albeit forced by the Ankylosaur Monster.
Garnet ended up stranded on the Jungle Moon after escaping the White Diamond Space Station, and for the 24 hours there, she had to lead everyone to finding the Jungle Moon Base. During this time, she was left in such mixed emotions over the "revelation" about Pink Diamond from White Diamond, beginning her doubt and worry in her Future Vision. When they were rescued by Blue Diamond, Garnet went off home to the Crystal Temple, finding the Crystal Heart barely functioning, and the temple empty much to her dismay.
Garnet began to start "acting random" from there on out. Much of her actions from there include; working as a director for the Ponyville theater, briefly working as a Big Donut employee, giving away pizza to Beach City, challenging Emerald to a robot fighting match, and so on. During this, she left to another world, and met up with Hoppy and Hopper for a Gem-based mission, using it as a test of her actual strength and see if she really was losing her talent. When the Tindalos first appeared, she froze up completely, finding their existence impossible as she just made them up prior to meeting them, causing Sniper's Father to split her up. She reformed afterwards, and admitted her weakness to everyone else, finally realizing that she wasn't considering Humans and their strength, and Steven Universe's maturity.
When she found out about Pink Diamond's true story, Garnet became so distraught she split up over it. She was not seen until the very end of the season, Ruby and Sapphire fusing at their wedding.
White Diamond Arc
She fully appears again during the festival itself, being one of the minds behind the festival. During the festival, she met with two other Jades, and helped them stand up to their superior in order for them to remain as Lemon Jade during the festival as they enjoy fusion so much.
Throughout much of the Grogar Arc, she played more of a supporting role in making sure everyone was prepared for their return to fight Grogar's Army. Shortly after her return to Earth, she quickly tried to convince Flint to form Nephrite in order to heal many of the corrupted Gems on Homeworld, to which Flint keeps refusing. Garnet grew more and more agitated towards him until she lost patience and attacked him. Steven is forced to intervene, pointing out how she was wrong for trying to make Flint and Jade fuse in spite knowing how important and special fusion is to her. The next day, she and Flint confront eachother and after hearing how much Flint admired her perfection, she revealed to him how flawed she truly was, and that she struggled so much to keep together because of the impact she had on everyone, admitting she wanted to be more like Flint too.
During their invasion onto Tambalon, she finds Stevonnie fighting Grogar and she quickly split apart from the group in order to reach them. Upon arriving, she finds that Stevonnie wanted to finish him off for good, and she quickly tried her best to make her stop. In the end though, she was thought to have been shattered by Stevonnie as a trick by Grogar.
My Little Universe II
Garnet herself doesn't technically appear until after the chapter "Tongue-Tied", due to both Ruby and Sapphire being rejuvenated by Spinel, and not fused during the time. When she did return, the first thing she did was find Spinel, who at the time was guilty for nearly causing a war between Equestria and Yakyakistan, and show her how Rutherford was having a good time in Ponyville despite her mistakes.
She joins the Harmony Gems in both the following court session to get Discord and White Diamond's magic back, and the final main battle between them and Grogar's Army. Just before the main battle in the Realm of Corners, she joins the original Crystal Gems and Elements of Harmony to take out the weapons located on Homeworld, but she sees Grogar coming and makes the group stop just before they got caught by Grogar and forced into fighting him. In the fight, she saves Steven by throwing him aside, telling him that they all love him, before she and the others tragically get shattered. She and the rest were revived and reformed afterwards within the Supreme Kindergarten and join to stop Grogar's army from leaving Homeworld.