Who is the main villain in the sequel trilogy who wears a mask early on?

The sequel trilogy’s primary antagonist begins as a masked enforcer of the First Order, leading the Knights of Ren and wielding a crossguard red lightsaber. That distinguishes him from Darth Vader (the original trilogy’s villain who dies before these events), Supreme Leader Snoke (his largely unmasked master who manipulates from the shadows), and Boba Fett (a bounty hunter, not the saga’s central foe). Born Ben Solo—the son of Han Solo and Leia Organa and once Luke Skywalker’s apprentice—he’s defined by inner conflict between light and dark. His mask, a deliberate echo of his grandfather Vader, represents a crafted persona; he smashes it in The Last Jedi and reforges it in The Rise of Skywalker, visually tracking his struggle with identity and allegiance.