SENSUNTEPEQUE, El Salvador — Karla Avelar had a backache when she reached the Sensuntepeque Penal Center, a cluster of cinderblock buildings perched on the side of a lush green valley near El Salvador's border with Honduras. So, after lunch, she took off her shirt and lay facedown on the cement floor of a room that doubles as activity space and cafeteria. Five women in bright makeup gave her a head-to-toe massage. They used hand cream as massage oil and placed a small candle over the knot in her back to draw out the pain.

Avelar was so at ease inside the prison that it is hard to imagine that she was regularly raped and tortured while she was incarcerated there between 1996 and 2000. Avelar, now 37 years old, was one of the many trans sex workers from San Salvador, El Salvador's capital, who has done time there over the past several decades. The ones who passed through there around the same time as Avelar report being abused by guards and pressed into a kind of slavery by the gangs who controlled the prison.

Those days are over, thanks in part to a legal complaint Avelar herself filed after her release. The women who rubbed her back on her recent visit, just before Christmas, are among the roughly 50 inmates who live in Sector 2, a special unit that houses trans women along with a handful of gay men. They still interact with the other prisoners in some common areas — several of them have boyfriends in the men's unit, and the prison supplies them with condoms — but they live and sleep in a part of the prison that is walled off from the men's unit for their safety.

"Today there is no rape," said one 25-year-old inmate who gave her name as Kendra. Kendra said she was subject to some verbal abuse when she first arrived in 2010 — a guard forced her to kneel for two hours while hurling homophobic insults at her — but Avelar came to see her and helped put a stop to it. The sealing of Sector 2 in that same year coincided with a decision by the prison administration to move the gang members out of the prison, which also went a long way to improving the trans and gay inmates' situation.

Many of them have stories much like Avelar's: Thrown out of home at an early age, they got by as sex workers, and survived rape or run-ins with gangs before landing in Sensuntepeque. They look to Avelar as a cross between a godmother and an advocate, able to win concessions from the prison administration that they could never get on their own. During the December visit, Avelar delivered a petition from the residents of Sector 2 to the warden asking that they be allowed to join the women's unit for a Christmas pageant. He agreed to it in writing on the spot.

"They're a little afraid of me because I've gotten them to remove certain guards," she told BuzzFeed News during the three-hour drive to the prison from San Salvador. "So with me, [the guards] are all like, 'Hello, Niña Karlita,'" greeting her with an affectionate nickname.

In a country where HIV and violence claims so many trans women's lives that there are few trans women in San Salvador over the age of 35, it's remarkable that Avelar is even still alive. She was raped and threatened with murder for the first time when she was 10, has survived at least three murder attempts as an adult, and has lived with HIV that went untreated for more than 13 years. Since 2008, she has run the trans rights organization she founded in San Salvador, known by the acronym COMCAVIS Trans. She regularly travels around the world to make the case for trans rights before international human rights bodies.

Avelar is part of a generation of trans activists in El Salvador, most of whom never finished primary school. They have won some substantial victories — including a directive issued by the government in 2010 prohibiting discrimination on the grounds of sexual orientation and gender identity in government jobs — even though human rights advocates consider El Salvador one of the most dangerous countries in the Americas for LGBT people. Based on media reports, COMCAVIS has documented at least twelve women and two gay men were killed in 2014, a figure they believe understates the actual number of murders.

"In terms of Karla's transformation, I can say, 'Wow, when I'm all grown up I want to be just like her' — only that she's younger than me," said William Hernández, who founded El Salvador's first LGBT rights organization in 1994, Entre Amigos (which translates to "Among Friends").

"We met her on the streets," Hernandez said. "We knew the comings and goings of all of the things she lived through." Now, he marvels at seeing her in meetings seated next to ambassadors and cabinet ministers. "And she's not just sitting there — she's actually expressing herself, making decisions and laying the cards on the table."

Avelar was born in Chalatenango, a rural district just to the northwest of the one that houses the Sensuntepeque prison. She left home when she was 10 years old, after the second time her cousin raped her in their family house. Another cousin used to shoot at her from time to time — and finally told her to get out.

"My cousin warned me that if I didn't leave home he'd kill me, because in his family there were only machos," Avelar said. She was dressing as a boy at the time, she said, but "I wasn't fooling anybody. ... In my town, in my neighborhood, everybody stopped calling me 'Carlos'; they called me 'Karla' instead. Or 'the faggot.'"

She left without enough money for bus fare, so she started walking toward San Salvador. She walked for a day and a half before reaching Apopa, a town just outside the capital, arriving at around 11 p.m. A man took pity on her and paid for her to take a bus the rest of the way. She spent the next six months sleeping in the San Salvador bus station or on the street, feeding herself from the trash.

She eventually saved up a little money from begging and bought a case of Coca-Cola, and began a business selling soda in one of the city's largest markets. There she met a woman named María who took her in but made her work a grueling schedule of domestic chores.

The woman's son also raped her, Avelar said, "but I stayed there because I didn't know what else to do."

One of her most dangerous chores was buying tortillas. María's house was in a neighborhood controlled by the 18th Street gang, but the tortillería was in territory of the rival Mara Salvatrucha (MS). On one of these tortilla runs, a group of MS members grabbed her and took her to a place where she said about 15 men raped her. There were more waiting their turn, but she found the courage to make a break for it.

She returned to homelessness shortly after. That's where she first met another trans woman, named Diana, who invited Avelar to come along with her when she worked the streets. Avelar discovered that sex work finally gave her a way to earn money on her own and a little bit of control over her life.

"I was young [and] I made money," she said.

Avelar stayed friends with Diana until about eight years ago, when Diana was killed by her partner, a police officer. They had no real name for what they were at the time they first met. Most of the trans women in San Salvador were lumped into the category of "homosexuals" or they called themselves "locas," which literally means "crazy women" but often is used to mean something similar to "fag."

"At that time, we didn't even know that we were 'trans' or that we were the subjects of rights or anything," Avelar said.

Many of the trans sex workers who were already working in San Salvador when Avelar entered the business in 1990 remember those years as the tail end of a golden age. A civil war raged in El Salvador from the early 1980s until 1992, but the capital itself was comparatively peaceful and home to a thriving red-light district where gay men were relatively open and trans sex workers enjoyed steady business from the soldiers and police. There were a few strips where they worked, but the center of activity was a four-block area known as the Praviana. The women who spent time there in the '80s and early '90s estimate that in an area of about four blocks, anywhere from 70 to 90 trans women lived, most of them sex workers in the neighborhood's hotels.

Avelar was too intimidated by the other trans women to work in the heart of the Praviana. The veterans didn't exactly welcome her with open arms — they bullied her ruthlessly, calling her "la machorra" ("the dyke") because she wore short hair.

The "trans women who had been there a long time … would walk up and steal my money — sometimes they would even leave me naked," Avelar said. Once, a woman waved a machete in her face and told her she "had a pretty face for slicing up into little pieces."

Avelar eventually learned to fight back, and she began dishing out the same kind of abuse to the women who had treated her so badly. But this was as the Praviana began to decline in the 1990s. Many of the women left for the United States, following a well-worn path that many Salvadorans took in the dangerous and unstable period as organized gangs tightened control of the country following the civil war.

And then there was the "Matalocas" — the "Trannykiller." A serial killer started attacking trans women on the street in a series of drive-by shootings. He was said to have a wooden leg.

A man matching his description nearly killed Avelar in 1992. One night, Avelar said, she got into the car of a john who drove her to a secluded part of town after agreeing on a price. Her heart stopped when she went to go down on him and discovered he had an artificial leg.

"I touched his peg leg and I got scared," Avelar remembered. "I said to myself, 'He's already killed me.'"

She tried to act calm and finished the blow job, but he had noticed her panic. He pulled her off his penis, smacked her across the head with the butt of a pistol, and then made her get out of the car. That's when "penetration occurred" she said, and then he forced her back into the car and promised to kill her if she tried to escape.