When Disney acquired Lucasfilm in 2012, they made the controversial decision to ditch the Star Wars Expanded Universe, otherwise now known as Legends, wiping out years and years of stories and references that many casual fans really didn't know much about to begin with. The decision was met with hostility by many hardcore Star Wars fans, but the choice has proven to be wise over the years. The Expanded Universe, or EU, was getting rather out of hand, so by wiping the slate clean, Lucasfilm is able to cherry pick what they want to bring back to become official Star Wars canon, and Solo brings back two obscure deep cuts from the EU. There are SPOILERS for Solo below, so read ahead at your own risk.
Solo: A Star Wars Story is currently in theaters and many fans find the film to be a fun movie that colors outside the lines of the regular Star Wars projects. There's the return of Darth Maul, which caught everybody off guard in a very pleasant way, but it has led to questions from casual fans who aren't aware of Maul's story after The Phantom Menace. Solo screenwriters Lawrence and Jonathan Kasdan went deep to bring the Cloud Riders gang from the EU and even took the time to put Warwick Davis' Weazel character from the prequels and place him in the gang, but those aren't the deep cuts that we're referring to.
The first of these obscure EU references in Solo comes from Emilia Clarke's Qi'ra character who explains how she was able to fight so well on Kessel with a borrowed cape from Lando Calrissian. She explains that she used a martial arts technique called Teras Kasi. While that name might not ring a bell for everybody, some diehards recognized the name from a terrible 1997 PlayStation game called Star Wars: Masters of Teras Kasi. The game was made by LucasArts and was an attempt to get into the fighting game genre with the use of Star Wars characters, but is more known for being notoriously horrible. So, it was a pretty funny surprise to see that name come up in Solo to become official canon.
The next obscure EU reference in Solo comes after Han Solo and crew flee Kessel with the Unrefined Coaxium. In order to save the ship and its crew, young Han Solo has to fly through Akkadese Maelstrom, getting really close to the Maw. In the EU, the Maw was introduced in the Jedi Academy books and is a cluster of blackholes in the Maw Nebulae. It's also the area where the Empire has a secret base where they built the Death Star prototype as well as other super weapons included in the EU. The intense gravitational pull of the Maw in Solo makes it appear that nothing could ever survive after getting sucked into the Maw, which has raised some questions.
One of the main questions concerning the Maw in Solo: A Star Wars Story is how the Imperial Star Destroyer finds the Millennium Falcon when it leaves Kessel. Many believe that the film is taking something more from the Maw, maybe insinuating that the Empire does have a secret base there where they are making super weapons. At the very least, it seems that Lucasfilm has planted the seed that the Maw could be around in the future of Star Wars. Solo pulled some pretty interesting deep cuts from the EU and you can read more about the Maw and Teras Kasi at Mashable.