A wave of rifts between parallel universes that the USS Cerritos was assigned to close during the final season of Lower Decks, ending with a permanent gateway beside Starbase 80.
The quantum fissure crisis is the running story of the fifth season of Lower Decks. In Dos Cerritos the ship is pulled through a rift and meets a harsher version of itself, and Starfleet then gives Captain Freeman the task of sealing the fissures.
Fissure Quest follows William Boimler, Brad Boimler's transporter twin, who commands the Anaximander with a crew of people gathered from other realities. He is hunting whoever is making the holes, and finds an alternate Lily Sloane, captain of a ship exploring the multiverse. A resentful alternate Harry Kim then sets off a reaction that could destroy every universe.
In The New Next Generation the energy reaches the prime universe as a wave that alters whatever it touches. The Cerritos crew shape it into a single stable rift, Freeman takes command of Starbase 80 to oversee it, and Jack Ransom becomes captain of the Cerritos.