WARNING: The following contains spoilers for Buffy the Vampire Slayer #26 by Jeremy Lambert, Marianna Ignazzi, Raul Angulo, and Ed Dukeshire, on sale now
Across the modern revival of Buffy the Vampire Slayer, an entire multiverse of slayers and monsters has been steadily introduced -- with the modern incarnation of the Scoobies even seemingly visiting the universe of the original show for a brief visit.
These multiversal adventures helped Willow and Buffy contend with the loss of Xander (who'd finally been fully corrupted into a vampire and was subsequently killed by Faith), and also unlocked other threats -- including setting up a multiversal level threat that, according to Anya, wants to wipe out every reality in the Slayer multiverse.
Among these other dimensional threats to the Scoobies are the Lurkers, the monstrous beasts that roam realities in search of people who don't belong so it can consume their memories. The Scoobies escaped the Lurkers while visiting an alternate reality largely unscathed, but Willow is surprised to discover that one is still following her even in her home reality as she researches more about dimensional travel. While she and Giles are still trying to figure out the full extent of the multiverse, it turns out that Anya has a deeper understanding of it -- which makes sense, given her previous travels to other dimensions. While speaking with Morgan -- the Slayer before Buffy who was secretly revived and has been working with her -- Anya reveals that there's a specific threat to the multiverse.
Anya has discovered that someone known as Silas is at the heart of the threat to the multiverse, and is the one controlling the Lurkers. He seemingly wants to bring about the end of all things, wiping out every world in the multiverse as part of some unknown scheme -- and effectively make him into the Buffyverse version of DC's Anti-Monitor. He's specifically looking for a "connecting point," where all the universes intersect. Anya seemingly knows more about Silas as well but doesn't get the chance to further explain the situation before Giles comes over to continue their research.
It's a major development for the series, giving the so-far unseen ultimate threat of the series a name. Notably, there was a Silas in the original Buffyverse, and although he wasn't a crucial villain he was an important one who also hopped across dimensions. Silas was introduced in the conclusion of Season 2 of Angel, during a story-arc that saw Angel Investigations relocated to the world of Pylea. Silas was the leader of the Covenant of Trombli, the ruling class of the dimension and secretly an agent of the demonic law firm Wolfram & Hart. His mission was to force an empowered princess from another realm (Cordelia) to sleep with their champion (the heroic Groosalugg), potentially stealing her visions from the Powers That Be.
Desperate to hold onto his power across the three-part storyline, Silas ultimately ordered the eradication of the human slaves to quell a revolt, but was stopped and beheaded by Cordelia. While he was a minor villain in the grand scheme of things, it's possible that this could be another, more ambitious version of the villain who can use pocket realities and dimensions to his advantage. Alternatively, this Silas could be an original and unconnected threat -- which the modern Buffy the Vampire Slayer has proven willing to utilize at various points, such as with the monstrous Hellmother. Regardless of the true nature of the threat, it's clearly a big enough danger to catch the attention of Anya -- and potentially bring about the end of the Slayer multiverse.