Runaways season 3 features a direct link to Agents of SHIELD season 4. These appear to be the last days of Marvel Television, with show after show cancelled or pulled from production altogether. As a result, Marvel appear to be attempting to tie the continuity of their various TV series more closely together than ever before, tying up the various loose ends.
All that makes Runaways season 3 particularly interesting. This season will see the teen superheroes team up with the stars of another (cancelled) Marvel series, Cloak & Dagger. They'll find themselves working against an extradimensional threat, the powerful sorceress Morgana Le Fey. The Runaways season 3 trailer suggests that Nico's mysterious Staff of One has somehow made her vulnerable to Morgana's terrifying influence.
On closer examination, the trailer also confirms a direct link between Runaways season 3 and Agents of SHIELD season 4. One shot shows Morgana at the center of an unknown ceremony, presumably an attempt to pierce the dimensional barriers between her realm and the Earth. The table bears an object that will be very familiar indeed to Agents of SHIELD viewers - the Darkhold, a mysterious book of spells.
Otherwise known as the Book of Sins, in the comics the Darkhold is the most dangerous spellbook ever created, fashioned by a demonic entity named Chthon. Agents of SHIELD season 4 revealed that it has been sought after by some of the most dangerous men in history, including Baron Von Strucker and the Red Skull. It had fallen into the hands of scientists who worked at Momentum Labs, and who realized the scientific basis for magic; that sorcery was, as the Ancient One put it in Doctor Strange, "the source code that shapes reality." The Darkhold's spells were used to rewrite the laws of reality itself, creating bridges between Earth and other dimensions.
This brief glimpse of the Darkhold serves as an important reminder that there is no clear distinction between advanced science and sorcery when it comes to the MCU. Nico Minoru may believe that her Staff of One is science-based, but it's even possible her parents worked with the scientists of Momentum Labs when they created it, meaning it could have been created using the forbidden knowledge of the Darkhold. If so, then it neatly explains the Staff of One's powers; it works by drawing energy from another dimension. In fact, it could well be tapping into Morgana Le Fey's dimension, and she's discovered it, realizing she could use it as a bridge.
This probably isn't the same copy of the Darkhold as seen in Agents of SHIELD, however; the Marvel timeline doesn't quite match up. Still, it's quite possible that Morgana Le Fey has her own copy. Again, referring to the comics, Morgana Le Fey was one of the people who studied the Darkhold in the ancient times of King Arthur, and she was the one who first had it bound as a book. It's entirely conceivable she created her own copy, and has been waiting for an opportunity to use it in order to jump from one dimension to another. The interesting question is whether this connection to Agents of SHIELD will lead to another cameo in Runaways - a Ghost Rider appearance or Easter egg of some kind. That show revealed Ghost Rider was drawn to just the kind of interdimensional disturbance Morgana Le Fey is creating, meaning she could well earn the ire of the Spirit of Vengeance.