And then there's the music. Run the Jewels debuted a new song from their coming album, Run the Jewels 3, in the Horde 3.0 premiere trailer, and that's not where this partnership ends. The song is called "Panther Like a Panther" and it kicks off a larger collaboration between Xbox, The Coalition and Run the Jewels.

The group's website has been taken over by Gears of War 4-branded shirts and sweatshirts. The clothes feature a mash-up of Run the Jewels' disembodied-hands logo and Gears of War's famous chainsaw gun, with shirts starting at $28 and sweaters at $65.

Killer Mike and El-P are also going to appear in Gears of War 4 as multiplayer characters, once the game comes out on October 11th.

Horde 3.0 will be playable at PAX West in Seattle, Washington, this weekend, and Run the Jewels will also be hanging around the city. Killer Mike, El-P and Gears of War co-creator Rod Fergusson will be promoting the new game at BAIT from 2PM to 3PM PT on Saturday, September 3rd. That same day, Run the Jewels is set to perform on the main stage at the Bumbershoot Music and Arts festival at 7:20PM in downtown Seattle.

Update: The Coalition studio head and Gears of War co-creator Rod Fergusson tells Engadget that working with Run the Jewels was a smooth, professional experience.

"For me, it was great working with them in the studio," Fergusson says. "They have been generous with their time and their talent. It only took one recording session each to get their combat chatter recorded for multiplayer and Horde, which is amazing given the effort required to record all of those lines. It was easy to tell that they are seasoned voices for that kind of work."

Xbox director of marketing Guy Welch says they ended up working with Run the Jewels because Killer Mike and El-P were on a similar creative wavelength as the Gears of War 4 crew. Welch first listened to Run the Jewels back when the new game was top secret -- even his manager didn't know what he was working on -- and the songs struck a chord with him.

"Like Delta Squad, here are two career guys from different backgrounds coming together almost at random on a project that's a total long-shot," Welch says. "And there's this sense of love and respect on every track for the traditions of hip-hop and the thrill of creating something together. I just knew that if we brought Gears back that we'd have to do something with these guys."