Alix Earle has been laying out puzzle pieces -- literally -- as to what her new brand is going to be after launching a mysterious account called "wtfisalixdoing" on social media ... and what she's doing is releasing a skincare line called Reale Actives, TMZ has learned.

According to trademark filings obtained by TMZ, the TikTok star is locking in the name for a beauty brand centered on skincare -- personalized by scrambling her last name -- signaling a major move into the cosmetics space.

The trademark points to a range of skincare products, suggesting this isn’t just a one-off drop, but a full-on brand play ... including "non-medicated and medicated skin care preparations."

Alix had fans scratching their heads for days with the cryptic account -- posting random content that didn’t seem to add up quite just yet -- but it now looks like it was all part of a calculated tease leading up to the reveal.

The move tracks for Alix, as she first blew up online by being brutally honest about her skin journey, showing fans it’s okay to go bare-faced through breakouts, and even documenting her experience with Accutane, an acne-fighting medication.

Bottom line ... the mystery has been unveiled!