WARNING: The following contains spoilers for Avengers Forever #4, now on sale from Marvel Comics.
For years, Peggy Carter was just a minor footnote in the overall history of Captain America. Her return to prominence following the success of Captain America: The First Avenger led to her being reinvented in the comics as a hero in her own right.
This carries over into Avengers Forever #4 (by Jason Aaron, Jim Towe, Guru-eFX, and VC's Cory Petit), which reveals that one of the major multiversal heroes working alongside Avenger Prime is another variant of Peggy as an analog for Captain America, further cementing her as one of Marvel's most popular alternate universe heroes.
The Avengers Forever series has been escalating the conflict between the multiversal Masters of Evil and an army of heroes grouped around the mysterious Avenger Prime. Some heroes such as Robbie Reyes and Earth-616's current Starbrand have been teased as future members of the group, in addition to the Deathloks already working with the team. But it seems that Avenger Prime has been recruiting other notable heroes as well, with the series now revealing two new allies in the form of Earth-818's Moon Knight and Vision. While fighting against an invasion of Red Skull variants from across the multiverse, the timely arrival of Robbie, embracing his destiny as the All-Rider, ends the battle although Moon Knight and Vision are lost in a multiversal gate.
Landing in the Center of Infinity, the two heroes are approached by three others who want their help. The trio all appear to be Avenger variants, with a 1602-style Hawkeye and an Iron Man whose armor is designed around Black Widow's color scheme and logo. Leading the three is Peggy Carter's Captain Britain, who appears to have taken a leading position alongside Avenger Prime. It's an exciting development, partly because it implies the mystery of Avenger Prime is close to being revealed, and partly because it continues the recent multiversal trend of reimagining Peggy Carter as the Sentinel of Liberty. Despite being a relatively new idea, Peggy Carter becoming Captain America has become a major fixture of the Marvel multiverse.
Peggy Carter first appeared as a variant of Captain America in the Marvel Puzzle Quest videogame. As part of a celebration of Captain America's 75th anniversary in 2016, a number of Marvel games created their own unique take on the character. Peggy proved popular enough to appear in the 2018 iteration of the multiverse-hopping Exiles series, which formally introduced her into the comics multiverse alongside a gender-swapped version of Bucky as her partner. The character later transitioned to the MCU in the inaugural episode of What If...?, setting up this variant as a major player on a multiversal scale.
Coupled with the release of a Peggy Carter-led Captain Britain series and rumors that Peggy may play a role in the upcoming Doctor Strange and the Multiverse of Madness, it's exciting to see this version of Captain America getting the spotlight that she deserves. Peggy Carter gaining the Super-Soldier Serum instead of Steve Rogers opens up the door for some interesting stories, and seeing her take charge of an entire multiversal force could be the perfect way to codify her credentials as a vital Marvel hero.