(This is for the fanfiction "Crossover Together". Info may change from canon information)
Envy usually appears as a pale-skinned androgynous youth with a lean, muscular build and bulging biceps. Envy has long, wispy hair, slitted eyes with violet pupils, and wears a black, form-fitting bodysuit and a matching headband with an alchemic, triangular symbol on it.
After being drained of his abilities, he takes the form of a true human being: a boy ranging from twelve to thirteen-years-old, has pale skin, violet eyes with slit pupils and shaggy black hair growing past the shoulders in back and growing down over the sides of the face, all the way to his collarbone in the front. He initially wore the same clothes he had as a Homunculus, and still keeps them on retainer, but was later given regular clothes by Blair.
Envy, much like other demons, had a dislike towards Humans and deeply enjoys killing and torturing them. As he followed Sombra, he is shown loyal to him and will follow his orders, albeit grudgingly, but his violent tendencies do make him more often than not go out on his own. Mostly this happens when he either finds a way to kill someone, or is looking for revenge on someone who wronged him. This is revealed later on to be from his jealousy towards humans, and how they're so compassionate towards eachother unlike most of those in the Underworld. This secret is his most precious one, and when revealed and found out by Tirek, was willing to take his own life away out of pure distraught.
After he was transformed into a full human, he at first was very conflicted about the situation, not willing to accept much help from Team Harmony. Overtime though, he started to become less hateful over mankind as a whole, as they've shown him compassion he had never had prior to this. His view on humanity turned into a more positive one as time went by, and he became willing to defend his new, more free life. This got to a point when he refused to return to his former Homunculus self, in spite of his fellow Homunculi. He considers himself stronger as a human than a Homunculus due to his freedom of choice, which he never had beforehand. He developed a closer bond towards his human friends, and willing to protect them for as long as he could, as he doesn't want to lose what friends he had left.
Despite his change, his need for vengeance still stemmed from both forms and his violent tendencies can come back up at times, shown in his efforts to get back at Emi Isuzu by making her his maid through blackmail, and of course his feelings towards Sombra after he stole his Philosopher's Stone.
A notable ability as a Homunculus, he is capable of disguising himself almost perfectly as another human or creature, and to disguise his voice to match his target as well. This makes Envy a very successful spy for Sombra's kingdom. When turned into a human, he's still capable of expert lying and some level of disguise, him looking almost exactly how he used to be when confronting Lust.
Ever since given a Philosopher's Stone by Nagisa after turning human, he is shown to be able to use a small form of alchemic power, namely in creating portals from the Surface world to the Underworld.
Envy was tasked to spy on Team Harmony and the E building by Sombra. Although ordered not to attack them, Envy found a loophole in Sombra's instructions saying he can't get caught while doing it, and he tried to kill them off anyway. After a number of failed attempts, he isolated Karma Akabane, and tried to kill him off before Korosensei showed up and ruined his plans. He was stabbed in the back by Karma's Miracle Sword, but he revived himself when they both left and raced off. Sombra confronted him directly, and he promised to kill any and all witnesses.
After given word of Team Harmony's departure, Envy was tasked for Demon recruitment in England alongside Lust and Gluttony. On his arrival, he took the form of a local crime lord, killing the original, in order to lure Team Harmony in and kill them off by kidnapping Ciel Phantomhive. He was later found out by Karma again though, and at first he was confident as Korosensei wasn't there, just to be stopped by Sebastian Michaelis instead. He was left with a humiliating punishment by Karma (putting mustard and wasabi up his nose). After the failed attempt he was found by Hellgar, and told to stick with the recruitment as he was in charge of killing them.
He took on a form of a young child later on, going out alongside Lust in disguise, him keeping the others busy by playing a game with them as Lust tried to get Sebastian to join up. They did succeed in that regard that night, and went out to collect some more. As he was out with Hellgar, he was then instructed to gather some humans for the demons' feast in Tartarus, a task he was willing to do more freely. When the Royal Ball began to come to fruition, he arrived disguised as Aleistor Chamber, and managed to isolate Aladdin from the others. He later used Aladdin's form as bait, and he managed to "kill" Blair as such. He and Lust thought they've finished off Team Harmony after the fact, but didn't realize their mistake until too late. Hellgar brutally punished them both for the attack, and were later put under attack on the Phantomhive Manor. He lured Bardroy and Grell Sutcliff outside, him taking form of Mey-Rin to do so. However, his attempt to kill them didn't work after the fight, she his body ended up severely burned.
His body was taken back to Tartarus, and he took a long time to heal in the Homunculi chambers. Once he was fully healed, he went out once again, this time towards Amestris. Once arriving at the capitol, he was tasked to spy on King Bradley and Selim Bradley, keeping form of an Amestris soldier. This kept up for the next following weeks until he was found out by Team Harmony, and apprehended. He was later released by Selim himself that night.
He was still roaming around Amestris when Pluton arrived and began destroying the city. Envy, despite insisting that he was on his side, was brutally attacked by Pluton, and launched miles away in a hit of Pluton's trident. He survived the landing, but Chrysalis found him there, and drained him of all his abilities and energy, making him pass out. He was found by Blair and Alphonse Elric, and taken in. He didn't wake up until after being brought to the Elric home, finding that he no longer had any of his abilities, and looked more human. He tried to escape, but was found outside by Sebastian, and brought back inside where the others explained what had happened to him, much to his confusion. He reluctantly stayed with everyone for the new few days to heal and recover. When he heard why they were doing this, eavesdropping on Ciel, he ran away to be sure they won't use him. He was found by Sombra and Chrysalis, and he tried getting his powers back, but to no avail. In fact, he was attacked, and later stolen of his Philosopher's Stone. He was shocked to find he was still alive, and realizing that he was all human. He fell into a breakdown shortly afterwards, but eventually was offered a place to stay with Team Harmony by Blair, which that time he accepted.
It was decided the next day that he would be enrolled in Class 3-E at Orora High School. At first he didn't work well with it, not showing up in uniform, and not getting along well with the other students. During a training session, he even threw one of the students at Korosensei just to get at him, which made the class angry with him. He stated that it didn't matter how he did it, and that they all wanted him killed away. When the group went off to the forest sometime later, Envy slipped away to find time to summon a demon to help him regain his powers, resulting in summoning Tirek. He tried to get him to give him his powers back, but Tirek forcefully tried to get his Philosopher's Stone, just to find it was not there. Tirek made to painfully clear to Envy through both physical and verbal abuse that he was pathetic, and his jealousy towards humanity made him even worse than most Homunculus, who were low in rank in the first place. This made him so distraught, he was ready to kill himself, just to be saved by the 3-E class. He was sent to medical care for a few days after the incident, and when he returned (in uniform), he admitted that he had underestimated humans and that they all were better than he thought, just to be told that he was just as good as they were now that he was a human.
Overtime, he continued to adapt to being a human being, and by the time Team Harmony had returned, Envy was given a place to stay by Hinano's family. Envy was enjoying his life as a human a bit more, but one day he found Heine Wittgenstein being bullied by Emi Isuzu. This got him to step up, and confront Emi, who which he physically assaulted as well before Emi pummeled him. This sparked him to try and get revenge on Emi Isuzu for a while.
As he was trying to figure it out, he discovered near Hinano's home that Lust had returned. Worried they would kill her and Nabiku, he quickly went out in his normal outfit, making it look like he hadn't changed at all. He lied to Lust, saying that he was on spying duty and the humans in the home he was going to take care of in just a bit. It was just enough to save the others. According to Nagisa Shiota's visions, he was told that he was going to end up being captured by other Homunculi, leaving him wondering if the others were going to be alright.
Eventually his drive for revenge lead him to Emi's home. He found Emi Isuzu in her true form, and took a picture of her. He got her to work for him as his personal maid under the risk that her secret would end up going out if she didn't, Envy enjoying every bit of it until she was found out by Niji. Envy didn't see what the problem was, but eventually his friends managed to convince him to go back and apologize. He went to Emi's home again, and apologized for what he did to her, though he admitted that he didn't see it as that big of a deal. Emi told him that she was worried over what others would think of her if they would find her out, and while he didn't think it was as bad compared to what he had gone through he still found it something to relate to. He made it clear that the picture was gone and that she had nothing to worry about anymore, even saying that her normal form was "overrated", and that her true form was something different. He left her soon after that on that note.
He was found sometime later by Gluttony, who he tried to get off his back and telling him that he was weakened by the Pluton incident. He went on saying he didn't know how to fix this, just for Gluttony to rush off with an idea in mind much to his horror. He quickly barricaded himself in Hinano's home, not willing to go back to his former life, when Nagisa found him. When explained his plan, Envy gave Nagisa his Homunculus outfit, and helped him look the part for his plan to work.
After the incident, Envy began to see what he thought was Lust roaming around Tokyo, believing at first to jot it up to home-sickness. He was found by her later on, and told that she wanted to learn to be more human like him. Envy decided to bring her to the E class to give her a headstart. Sometime later however, he somehow found Hinano advancing on him, which Envy began to realize who it truly was and knocked her off the bed. His suspicions were proven true when Chrysalis turned back to normal. He tried to kill her, but was knocked out cold after he hesitated, thanks to Chrysalis taking the form of Nabiku. He woke up in an alleyway, found by Terasaka's gang, and when he remembered what happened he quickly rushed back to find Hinano injured. It wasn't until then that Chrysalis and Lust were the same person. After Chrysalis was handled, he left her hanging in a tree, using salsa and hot sauce in a similar manor to what Karma would do, and left her there for the next few days.
When he got word about what happened to Team Harmony, he got the idea to go with Nagisa, Blair, and Aladdin into the Underworld to get the team back. He arrived alongside Terasaka's Gang, and Rio Nakamura. In his travels through the Underworld, he helped the group in figuring out where they were, and how to get to Abaddon, his knowledge remembered from his time as a Homunculus. He kept his support throughout their travels, and when they did reach Abaddon, it was him and Kirara who went in to find the group. While they were going through, he split apart from Kirara to try and kill Sombra himself, blaming him for all this trouble he'd gone through. He wasn't successful in his task, and ended up alerting the guards to his presence, but the release of the Great Tengu gave him enough time to slip by and rejoin Kirara. He joined the rest of the team in escaping Abaddon.
during the final fight, he was tasked in leading the Assassination squad to Sombra himself, as he knew the palace best. On reaching the Homunculi chambers however, he and the others were confronted by Pride, who he faced directly and gave the others time to pass him. He told Pride that Sombra was working him out, and he will toss him aside once he ran out of use, angering the first Homunculus. He was close to getting killed but, remembering Blair's words, he gathered enough strength to break out of Pride's grasp. He removed Pride from Selim, and found him as a fetal child. He left the Underworld with Pride in hand, wishing the others good luck.
His view on Team Harmony, as with many other Demons and Homunculi, were at first rather low, and he was more than willing to go in and kill them when he would be given a chance. After his first failed attempt, he was even more willing to kill them all, even defying Sombra's orders to do so, but after he was turned into a human, he found it very conflicting when the same team rescued him. His current views on Team Harmony are far less dangerous, as he was willing to go with Nagisa Shiota, Blair, and Aladdin back to the Underworld to rescue the rest of the team.
Lust and Gluttony both were his fellow Homunculi while he worked with Sombra. As fellow Homunculus, he had a more fair relationship with them both, and considered them better than other demons, often working with them when not on spy missions. He still cared for them after turning into a human being, but wasn't ready to tell them about his human friends. It's unclear as to his current standpoint on them.
Hinano is a fellow 3-E student that he had met while he was in Korosensei's class. He holds a closer bond to her than the other students, as it was her family who offered him a home sometime after he arrived and got settled in.
While not as strong of a bond as with Hinano, he has been shown to hang out in their group on occasion. His most notable relationship is with Kirara Hazama, who introduced him to "The Court of Monte Cristo", and her interests in demonic activity give them both something to share with. He also brings Terasaka's Gang with him when going to Abaddon.
As with many of his followers, Envy considered him higher up than himself, and will follow his orders, but he was a bit more reckless and reluctant with some instructions as they conflicted with his own needs and wants. He fully lost all loyalty towards him after being turned into a human, and blamed him for all of his trouble instead of blaming himself, even after Sombra pointed it out to him.