I'm not talking about the message boards, I'm talking about the Ten Rings. The terrorist group..... historically associated with the Mandarin. Officially, they're dormant, but evidence suggests that they're becoming move active.
~ Jackson Norriss about the Ten Rings.
The Ten Rings are a terrorist organization and a recurring antagonistic faction of the Marvel Cinematic Universe. It serves as the main antagonistic faction of Iron Man and the short-film All Hail the King, and a minor antagonistic faction in Iron Man 2, Iron Man 3 and Ant-Man. It is set it to return in the upcoming 2021 film Shang-Chi and the Legend of the Ten Rings.
Iron Man (2008)
While Tony Stark is in Afghanistan to demonstrate Stark Industries' new Jericho missile, a group of terrorists attack the convoy he is on, killing everyone but Stark. He is kidnapped by the terrorists (led by Raza), who introduce themselves as the Ten Rings. They demand that Stark build a Jericho missile for them. He refuses, so they begin to torture Stark.
Hours later, the terrorists show off a huge stockpile of weapons - all made by Stark Industries. Tony appears to relent and start building the missile, but has other plans. With the help of fellow captive Yinsen, Tony constructs a tiny device called an Arc Reactor - a new type of power generator - streamlined from a much bigger design used in one of his companies factory. The power output is enough to run Stark's heart for fifty lifetimes... or something much bigger for about fifiteen minutes.
Tony designs a way out for himself and Yinsen - a powered weapon suit that he will wear and use to defeat the terrorists. Midway through construction, the apparent head of the Ten Rings, a man named Raza, arrives and attempts to torture Yinsen, angry because he thinks Stark is not working on the Jericho as they wanted. Raza gives them one more day to finish.
Working overnight, Yinsen straps Tony into the completed armored suit, telling him the way out of the cave. They set off a bomb inside the cell as a distraction for the guards as Tony powers up his suit. Yinsen realizes that they will not have enough time. He grabs a gun and runs off to distract the surviving guards.
Tony, fully powered, muscles his way through the cave. The guards try to stop but his suit easily deflects their weapon fire. Halfway out, Stark finds Yinsen, mortally wounded. Tony tearfully thanks Yinsen for saving him, and Yinsen encourages Tony to not waste his life as he dies. Tony turns his suit on the terrorists, igniting flame-throwers. He destroys their stockpile of weapons and uses a rudimentary jet-pack to blast away from the captive zone. The armor is ruined as he crash-lands into a sand dune, but he escapes alive.
Months later, Tony learns that the Ten Rings is using weapons created by Stark Industries to terrorize the Middle East, and that Obadiah Stane was dealing them weapons behind Stark's back. Stark dons his Iron Man suit for the first time and flies to the Middle East. Within seconds, he defeats the terrorists the armors superior targeting allows him to kill a group using civilians as human shields without harming the hostages and destroys the weapons they had obtained. The leader of the group tries in one of the buildings to hide only to find a red and gold arm smash through the wall and yank him back out into the street Iron Man then hands him over to the villagers saying "He's all yours." before taking off.
Not long after this, the Ten Rings are visited by none other than Obadiah. It is revealed that Stane paid the Ten Rings members to kill Stark, but they realized who Stark was and demanded a much higher price. After killing Raza, Obadiah takes the remnants of the Mark 1 armor they have gathered.
In Iron Man 3, Aldrich Killian uses the Ten Rings name, and hires drunken British actor Trevor Slattery to use The Mandarin persona to mask his failed Extremis experiments as purposeful attacks on the military.
All Hail The King
After Aldrich Killian dies, and Trevor Slattery is placed in Seagate Prison, an undercover Ten Rings agent, Jackson Norriss, breaks Slattery out of prison, and informs him that the real Mandarin wants to meet him after Trevor made a mockery of his beliefs.
As Darren Cross was holding an auction for his Yellowjacket suit at the Pym Technologies headquarters, a buyer working for both HYDRA and the Ten Rings was seen attempting to buy it. As Ant-Man entered the room, a fight had ensued with the buyer being knocked out and later killed when the building imploded.
Since Aldrich Killian and Trevor Slattery had no associations with the terrorist organization, and the real Mandarin is the true leader of the Ten Rings and has not fully appeared, the Ten Rings could possibly serve as the main antagonistic faction in the entire MCU after Avengers: Endgame.