With a huge online following, Big Londini has taken it upon himself to fight trolls - but isn't that TikTok's job?
"We will reclaim social networks from bullies, pedophiles, fraudsters and trolls."
A masked man in a black hooded sweatshirt speaks to the camera in an electronically distorted voice.
He looks and sounds like he's straight out of a horror movie.
But his goal is not to scare, unless you are an anonymous troll and cyber bully.
In that case, it will become your worst nightmare.
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In one of the videos, he points to an aggressive comment left on a woman's TikTok account.
"If some unknown person said this to your daughter, mother, sister, wife, what would you do?
"We have a habit of saying: stupid game, stupid prize."
And it's a regular postman of Greater Londini, an internet movement that became so popular on TikTok that it gained two million followers in just a few months.
The "game" is online trolling, and the "reward" is to be found by Great Londini.
If you're a troll, you might think you'll be safe behind your anonymous account name.
But Londini starts from the premise that it can reveal your true identity within seven to eight clicks.
If you are a child, they will tell your parents or your school that you are bullying people online.
If you are an adult - perhaps someone who posted a sexually threatening comment on a video of a child - then you will be seriously sued.
This may mean notifying your employer or your local police station.
It's vigilantism in moderation, where users of the platform take it upon themselves to try to clean up the app.
But that's not something TikTok is too happy about.
Greater Londini has had nine accounts permanently terminated so far, and the tenth has been suspended multiple times.
The platform rules that Londini was accused of violating ranged from online harassment and bullying to even violent extremism.
But Londini disputes all that.
"Until every bully, racist and scammer is kicked off the app, we're not going anywhere," he says in one clip.
"We are anti-trolls"
So who is hiding behind the mask?
He is known as Leo.
That is not his real name, and his identity is a well-kept secret because he regularly receives death threats.
Leo, however, occasionally takes off his mask in his live performances on TikTok, where he chats with both fans and critics who want to debate him.
And, moreover, Leo is only the public face of the volunteer movement with a mixed background in the military, cyber security and ethical hacking.
Speaking to me from an undisclosed location in the US, he tells me: “We are anti-trolls. If you're active right now on TikTok, someone is trolling you."
But isn't content moderation TikTok's job?
"They don't do that," says Leo.
"We tell TikTok everything. We send TikTok all the information, we report the accounts."
TikTok says it is making great efforts to protect users and has introduced new features such as allowing users to choose who can comment on their videos and to filter certain words in comments.
"We know there's no end goal when it comes to protecting our users, which is why we'll continue to invest in our teams, products and features to make sure TikTok is a safe place for our community," the spokesperson said.
The platform faces a mammoth task when it comes to content moderation.
According to TikTok, they removed 61 million clips in the first quarter of 2021 alone, and 91 percent of them were removed before being reported by a user.
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Origins in tragedy
Londini's mission to confront the trolls was born out of tragedy.
Last year, the 14-year-old autistic son of one of Leo's friends took his own life.
"After a while, a friend of mine, after the initial grieving period, reached out to us and said, you know, part of the reason he was so depressed was because he was being bullied a lot on social media."
At his father's request, Leo and several of his friends found the anonymous bullies who were torturing his son.
"We were able to give him that information and say, hey ... here you go and do what you want with it.
"And he turned to their parents and got, to the greatest extent, some kind of comfort."
The group of friends didn't stop there.
Under the name Great Londini - a mix of Houdini and Linux, the operating system - they decided to continue the work and concentrate on TikTok.
Fans of Greater Londini are so dedicated to their work that they tag accounts under videos and comments all the time, hoping that Leo and his team will take another troll to task.
But such fandom has its price.
There is a risk that the movement will at times become the very thing it despises.
Some followers are so violent that they become bullies themselves, which violates Greater Londini's rules - just like TikTok's Community Participation Guidelines.
The BBC spoke to a TikTok user who became the target of online abuse after Greater Londini criticized her Remembrance Day videos.
Liz, a peace activist, described the holiday when the US honors men and women who have died serving in the military "as a whole holiday dedicated to murder".
This caused violent reactions. Liz says she was bombarded with abuse, mostly from users with Londini in her username, who advised her to kill herself, and contacted her former employer in an attempt to persuade him to fire her.
"It really seems hypocritical that they're an anti-bullying account, and a lot of their followers are bullying people on the platform," says Liz.
Londini kicks users out of their network if they break the group's rules and Leo - who served as a US Marine - seems somewhat contrite about what happened to Liz.
"I understand their passion, especially when it comes to veterans," he says.
"But we try to set a good example. We are not abusing her - I wish the woman the best."
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